Merge pull request #6 from smarkets/master

Handle file objects without encoding attribute set
Mention recent bugfix (#6) in the changelog
Make 'make coverage' more concise
Hook up coveralls.io
Fix tests on Python 3.3/3.4 when run under coverage

As far as I understand, coverage somehow has the side effect of
instantiating the locals() dict of every frame, which then show up on my
backgrefs graphs, uninvited.  (Normally Python's fast locals optimization
keeps them empty.)

Exclude them explicitly.  This should fix Travis builds.
Add a coveralls badge
Improve test coverage

I'm pretty sure only Python 2.5 and older compatibility bits remain
untested (and I can't test those on Travis).
Mark Python 2.5 and older code with pragma: nocover

This is maybe cheating a bit, but the effort required for building
ancient Python versions from source just so I could run tests on Travis
is too great (and mocking (un)bound methods with im_self/im_func
attributes on newer Pythons seems somewhat pointless).
Improve test coverage a little bit

I was wrong when I thought only Python 2.5 compat code remained
untested.  There's also that early stop when reaching a module in
show_backrefs(), and all the subprocess spawning logic in show_graph().
Shameless self-promotion
Fix tests under Python 2.4 and 2.5
Release 1.8.1
Post-release version bump
New subversion complains if I svn add a file already in svn

This is bloody inconvenient and I should migrate ~/www to git.