Merge branch 'tests'
Merge branch 'tests'
Add Travis build status to README
Make all calls to print function calls
Fix calling lambda with parens

SyntaxError in python3.
Fix imports for Python 3
Import print_function from __future__ for Python 2 to use file
Remove tuple parameter unpacking from itag lambda
Cast zip to a list -- it can't be subscripted in Python 3.

It can't be subscripted because it is an iterator.
Change filter to listcomp, as filter is an iterator in Python 3.

We need this because we subscript it.
Read the sample API output file as a bytes object

In Python3, the API input is a bytes object, but the file is read as a
str. This makes them both match for both versions.
If testing, add the itag to the end of the list before sorting.

Python 3 changed the way sorting works for functionally identical
objects. We add the itag at the end to make them unique so that the
sorting order is always the same, which means we can easily test that
the function works as expected. This is not required in normal use,
because we don't care which order identical itags are returned in
relative to each other.
Add Python 3.2/3.3 to Travis YAML
Use system python, don't force to python2
Remove spurious print from testing
Merge branch 'python3'
Remove comment in README about video quality which is no longer true
Merge branch 'documentation'
Make all itag testing heuristic.

This makes tests still relevant on updates, and means that we don't have
to add the itag for each itag key (which would otherwise be needed on
Python 3+).