No support for "Between ... and ..."

[lsma]

Hey! I really appreciate this module. I've forked it and am trying to add support for strings like "Between September 12th and 22nd, 1914." I've gotten this to work by just adding "between" to ignoreable_chars and "and" to separator in create_parser. However, this lets in stuff like "January 12th and February 13th" which doesn't make much sense. Is this alright with you, and if so, should I go ahead with a pull request?