Update to use bundler and work on Ubuntu Trusty.

Switching to bundler saves confusion about gem paths when running
sass/compass to compile the CSS.

Trusty can use precisely the same packages as precise, with a few tweaks
to generalise the contents.
Remove liberror-perl and libsoap-lite-perl.

Try and save other people the potential pain of installing SOAP::Lite;
only UK FixMyStreet and Zurich geocoder use it, so set it as an optional
feature in the cpanfile instead.
Remove unused variable.

Also, s///r isn't present in 5.10, and FixMyStreet should still install
on squeeze.
Reinstate some cpanfile.snapshot entries.

This puts back any missing snapshot modules removed in
1708bc30af7176f95f0ec5718289d3a633daf32b, as they are required for
installation on squeeze, which misses or does not have the required
version of these.
Merge branch 'trusty-tahr'