Remove non-existent logging bit that sneaked in

Those are related to logging changes in Evernote’s fork that we did not
pick, I failed to remove those while merging which broke submitting
translation! If we decided to pick the new logging code, this commit
should be reverted.
cache: Cache the top stats for a much longer time

Previous behaviour had us cache for x*POOTLE_CACHE_MIDDLEWARE_SECONDS
which is 10-15 minutes by default. That is ridiculously quick for
something that is very expensive to compute and doesn't change that
much.
By default we now cache for a whole day and this can be changed in the
new setting TOP_STATS_CACHE_TIMEOUT.
settings: Document POOTLE_TOP_STATS_CACHE_TIMEOUT
travis: compile all Python files

Catch syntax errors early, especially in files that we might not test
during installation.
PEP8: W191 indentation contains tabs
Py26: with doesn't support multiple contexts

Unfortunately with does not support multiple contexts in Python 2.6 see
http://stackoverflow.com/a/12141070/2167584

So converted this to nested with statements which should work on all
supported Python versions.
Make this check more clearer