Start of unittesting

[ashcrow]

This PR adds the start of unittesting and is compatible with both Python 2.7 and 3.x. It also includes updates to .gitignore for python and test related files.

$ nosetests -v --with-coverage --cover-package=pykube test/
Verify cluster works as expected. ... ok
Verify clusters works as expected. ... ok
Verify contexts works as expected. ... ok
Test Config instance creation. ... ok
Verify set_current_context works as expected. ... ok
Verify user works as expected. ... ok
Verify users works as expected. ... ok

Name                Stmts   Miss  Cover   Missing
-------------------------------------------------
pykube                  0      0   100%
pykube.config          87     15    83%   134, 143-148, 154-158, 164-169
pykube.exceptions       4      0   100%
-------------------------------------------------
TOTAL                  91     15    84%
----------------------------------------------------------------------
Ran 7 tests in 0.028s

OK