README: Switch to markdown, provide more installation instructions

README

-efa - unofficial efa.vrr.de command line client
------------------------------------------------
-
-* <http://finalrewind.org/projects/Travel-Routing-DE-VRR/>
-
-
-Dependencies
-------------
-
- * perl version 5.10.1 or newer
- * Class::Accessor
- * Exception::Class
- * LWP::UserAgent
- * XML::LibXML
-
-
-Installation
-------------
-
-From a release tarball:
-
-$ perl Build.PL
-$ ./Build
-$ sudo ./Build install
-
-From git:
-
-$ perl Build.PL
-$ ./Build
-$ ./Build manifest
-$ sudo ./Build install
-
-See also the Module::Build documentation.
-
-You can then run 'man Travel::Routing::DE::EFA'.
-This distribution also ships the script 'efa', see 'man efa'.

README.md

+# efa - Commandline Public Transit Routing Interface
+
+efa is a commandline client and Perl module for EFA public transit routing
+interfaces such as [efa.vrr.de](https://efa.vrr.de). See the
+[Travel::Routing::DE::VRR homepage](https://finalrewind.org/projects/Travel-Routing-DE-VRR/)
+for details.
+
+## Installation
+
+efa has been packaged as
+[libtravel-routing-de-vrr-perl](https://packages.debian.org/search?keywords=libtravel-routing-de-vrr-perl)
+for Debian, so you can install it using your package manager of choice on
+Debian-based Linux distributions. It is also available as
+[perl-travel-routing-de-vrr-git](https://aur.archlinux.org/packages/perl-travel-routing-de-vrr-git/)
+in the archlinux User Repository (AUR). Both provide the commandline client and
+the Perl module.
+
+If you are using another distribution and/or would prefer a more recent
+version, you have four installation options:
+
+* Nightly `.deb` builds for Debian-based distributions
+* Installing the latest release from CPAN
+* Installation from source
+* Using a Docker image
+
+Except for Docker, __efa__ is available in your PATH after installation. You
+can run `efa --version` to verify this. Documentation is available via
+`man efa`.
+
+### Nightly Builds for Debian
+
+[lib.finalrewind.org/deb](https://lib.finalrewind.org/deb) provides Debian
+packages of both development and release versions. Note that these are not part
+of the official Debian repository and are thus not covered by its quality
+assurance processes.
+
+To install the latest release, run:
+
+```
+curl https://lib.finalrewind.org/deb/libtravel-routing-de-vrr-perl_latest_all.deb | sudo dpkg -i -
+```
+
+For a (possibly broken) development snapshot of the Git master branch, run:
+
+```
+curl https://lib.finalrewind.org/deb/libtravel-routing-de-vrr-perl_dev_all.deb | sudo dpkg -i -
+```
+
+Uninstallation works as usual:
+
+```
+sudo apt remove libtravel-routing-de-vrr-perl
+```
+
+### Installation from CPAN
+
+Travel::Routing::DE::VRR releases are published on the Comprehensive Perl
+Archive Network (CPAN) and can be installed using standard Perl module
+tools such as `cpanminus`.
+
+Before proceeding, ensure that you have standard build tools (i.e. make,
+pkg-config and a C compiler) installed. You will also need the following
+libraries with development headers:
+
+* libssl
+* libxml2
+* zlib
+
+Now, use a tool of your choice to install the module. Minimum working example:
+
+```
+cpanm Travel::Routing::DE::VRR
+```
+
+If you run this as root, it will install script and module to `/usr/local` by
+default.
+
+### Installation from Source
+
+In this variant, you must ensure availability of dependencies by yourself.
+You may use carton or cpanminus with the provided `cpanfile`, Module::Build's
+installdeps command, or rely on the Perl modules packaged by your distribution.
+On Debian 10+, all dependencies are available from the package repository.
+
+To check whether dependencies are satisfied, run:
+
+```
+perl Build.PL
+```
+
+If it complains about "... is not installed" or "ERRORS/WARNINGS FOUND IN
+PREREQUISITES", it is missing dependencies.
+
+Once all dependencies are satisfied, use Module::Build to build, test and
+install the module. Testing is optional -- you may skip the "Build test"
+step if you like.
+
+If you downloaded a release tarball, proceed as follows:
+
+```
+./Build
+./Build test
+sudo ./Build install
+```
+
+If you are using the Git repository, use the following commands:
+
+```
+./Build
+./Build manifest
+./Build test
+sudo ./Build install
+```
+
+### Running efa via Docker
+
+An efa image is available on Docker Hub. It is intended for testing purposes:
+due to the latencies involved in spawning a container for each efa invocation,
+it is less convenient for day-to-day usage.
+
+Installation:
+
+```
+docker pull derfnull/efa:latest
+```
+
+Use it by prefixing efa commands with `docker run --rm derfnull/efa:latest`, like so:
+
+```
+docker run --rm derfnull/efa:latest --version
+```
+
+Documentation is not available in this image. Please refer to the
+[online efa manual](https://man.finalrewind.org/1/efa/) instead.