Put most recent frames at the end

Sentry wants them that way ("Frames should be sorted with the most
recent caller being the last in the list." from
http://sentry.readthedocs.org/en/5.4.5/developer/interfaces/index.html),
and displays stacktraces upside-down without this change.
Add classname context to frames

This changes the stacktrace output on Sentry's site from this:

    core.clj in invoke at line 2515
to:
    core.clj in clojure.core$some.invoke at line 2515

The updated version gives enough context to debug further.
Merge pull request #6 from trptcolin/stacktrace_tweaks

Stacktrace tweaks