Allow the word size to be configured and minor usability updates

[jswencki]

• Added word_size configuration to allow words that smaller than 3 characters to be filtered. Also gives the ability to go up in size. Prior to this modification it was hard coded at 3. Default is 3 so existing implementations are not broken.
• Added new unit tests for word_size
• Modified unit tests to allow them to be run in RubyMine as well as command line as it is today.
• Updated gemspec so the version is pulled from the version file. This centralizes the version to one location.