Unicode only

It appears that pycaption doesn't handle string input in a fully correct manner as some of the conversion tests failed with no source editing after install. The tests that failed all were related to incorrect Unicode handling

Pycaption should only take in and output Unicode. The user should be responsible for the encoding and decoding of the data passed to pycaption. There should be no risks of passing BeautifulSoup4 Unicode either (see my comment in #18 for an explanation)

As a result, all string literals were converted to unicode literals. All tests now pass as well (before there were a few tests that failed out of the box as a result of Unicode encoding issues)