Skip articles and prepositions in titleize()

[tawdle]

Defines a dictionary of articles and prepositions, and leaves them in their lowercase form when calling titleize().

This leads to more typical titleizations.

[pksunkara]

@tawdle I am sorry but I can't accept this. A lot of people are using this library and this will be a breaking change for them. I would request you to maintain your own fork with this change instead if you want to use this.

Thanks.

[tawdle]

@pksunkara Fair enough. What if the new behavior were enabled by an optional flag, with the default preserving existing behavior?

[pksunkara]

I can merge that :)