Changed the TaggerFstCorpus class to be public
updates to the "LookupAttribute" (now TaggingAttribute) [SolrTextTagger Pull request 7](https://github.com/OpenSextant/SolrTextTagger/pull/7) based on feedback of [David Smiley](https://github.com/dsmiley)

* renames Lookup** to Tagging**
* adds a unit test for the TaggingAttribute