Add rabbi and cantor to list of religious titles

[benbalter]

Great project! This pull request adds rabbi and cantor to the list of recognized religious titles (like father or pastor).

I believe I did it right. I updated parser.y, ran bundle exec rake racc, wrote a test, and committed the results.

Testing locally, the titles are recognized as expected.

[coveralls]

Coverage remained the same at 97.81% when pulling 0b9c5e0 on benbalter:add-rabbi-and-cantor into eab5cb1 on berkmancenter:master.

[inukshuk]

Thanks!

Just a quick note that these titles are used by the lexer only; that means you don't need to recompile the grammar if they change and, more importantly, they can be changed dynamically. I say this because the matches in the title can be problematic (e.g., if you have proper names 'Pastor' or 'Rabbi' etc.). So the patterns in the options are really intended as examples and you may want to adjust them to your locale.