Suppress byte-compilation warning

This takes care of the byte-compilation warning
about a reference to a free variable `paredit-version`.
Fix a couple of docstrings and indentation errors.
Use should instead of assert in tests.
Docstring additions and fixes.
Simplify popup buffer quit/restore using `quit-window'.
Update copyright year and add link to contributors.
Fix #211 - implement jump to error from stacktrace

Now when someone gets a compilation error after `C-c C-k` the top error
of the stacktrace is clickable and it will take the user to the
offending line in the source code. This doesn't work when there is
no source file (say after eval last sexp) for obvious reasons. The functionality
relies on `compilation-minor-mode` being enabled in the error buffer (which is done
automatically after it's created).