Fix to code for initial caps at start of lines.

Now capitalize first character explicitly rather than using .title().
This prevents problems like "It'S".
Added swap files to .gitignore.
Allow caching of rhyme dictionaries in a local db.

Use cPickle to store the rhyme dictionaries build by rhymelib to a local file.
This prevents having to parse the corpora and build rhyme dictionaries on every
start of the library.

Also added code to autodownload the corpora if required.