Deprecated failUnlessEqual() -> assertEqual()

http://docs.python.org/2/library/unittest.html#deprecated-aliases
Deprecated failIfEqual() -> assertNotEqual()

http://docs.python.org/2/library/unittest.html#deprecated-aliases
Deprecated failUnlessRaises() -> assertRaises()

http://docs.python.org/2/library/unittest.html#deprecated-aliases
Deprecated failUnlessAlmostEqual() -> assertAlmostEqual()

http://docs.python.org/2/library/unittest.html#deprecated-aliases
Merge pull request #139 from zas/deprecated_unittest_aliases

Replace deprecated unittest aliases
pep8 fixes
Merge pull request #140 from zas/pep8

PEP8 compliance fixes
Use info dialog to display per-album error log.

When an error occurs during loading of a release, it will be visible
in info dialog for this release (which was unused).

New icon was added to mark visually releases with errors, and scrollbars
will appear in info dialog if needed.
Make modified releases a bit more obvious using a specific icon.
Display cover art errors associated with album if any
Switch tab title to Errors when needed.