add custom not_found and exception templates

<div class="row">

	<div class="col s12">

		<div class="card red darken-4">

			<div class="card-content white-text">

				<span class="card-title">500 Internal Server Error</span>

				<p>Das hätte nicht passieren sollen.</p>

			</div>

			<div class="card-action">

				<a href="https://github.com/derf/travelynx/issues" class="waves-effect waves-light btn-flat white-text">

					<i class="material-icons left">bug_report</i>Bug melden

				</a>

			</div>

		</div>

	</div>

</div>

<div class="row">

	<div class="col s12">

		<p>Angaben für einen Bug-Report:</p>

		<p style="font-family: monospace;">

			Timestamp:

			%= DateTime->now(time_zone => 'Europe/Berlin')->strftime("%d/%b/%Y:%H:%M:%S %z")

			<br/><br/>

			Message:

			%= (split(qr{\n}, $exception->message))[0]

		</p>

	</div>

</div>

<div class="row">

	<div class="col s12">

		<div class="card red darken-4">

			<div class="card-content white-text">

				<span class="card-title">404 Not Found</span>

				<p>Diese Seite gibt es hier nicht.</p>

			</div>

		</div>

	</div>

</div>