Fixed rounding test for centiseconds
Fixed unsyced centiseconds generation
Actually fix centiseconds test case
Partial support for tts namespace
Fixed namespace declaration on formatting attributes
Fixed tests for the correct namespace declaration
Fixed case with nested spans
Better support for nested tags inside styled els
Handled edge case with nested tags and empty values
Fixed error when root element is not a <tt>
Added support for legacy subtitles
Fixing youtube subs parsing when youtube data has no duration
Oops, removing debugging raise
Added test for ampersand scaping on srt files
Created method to update timming in place for subs
Make sure that begin or end as empty strings get treated as unsynced subs
Small doc improvements
And now commiting new test data file
Fixed storeage test.

I think that last code was a typo, there's no way that simply
accessing the to_internal method would raise an error.  This new test
passes.  It doesn't test the subtitle length, but I don't think
there's anyway to do that if there's a parsing error.
Use difflib for diffing.

This allows us to find insertions and deletions between the 2
sequences, instead of simply matching item by item.

This changes subtitle_data.  Now it's possible to have empty
SubtitleLines in the middle of the list, rather than only at the end.

This also changes time_changed and text_changed:

Before we calculated the number of differences using an item-by-item
comparison, then divided that by the length of the longest sequence.

Now we calculate using difflib's ratio() method.  ratio() calculates
the number of differences, multiplies by 2, then divides by the sum of
the 2 sequence lengths.

This should be the same if the sequence lengths match up, but if items
are inserted or deleted, then the numbers will be different.  I think
this is fine, since before if you inserted/deleted a subtitle, the old
calculation would give you a totally bogus number.