Fixed test_get_file_extensions() on Python 3.

(removed dependency on dictionary iteration order)
Corrected Typos

Fixed a spelling error and removed a double `import`
Merge pull request #223 from jxnl/patch-1

Corrected Typos
Merge pull request #221 from timgraham/test_get_file_extensions_fix

Fixed test_get_file_extensions() on Python 3.