Merge pull request #17 from westei/master

TagLL needs a public API to allow TagClusterReducer implementations
* Removed the `offsetAtt.startOffset() < lastEndOffset` term for checks if tokens are skipped. The assumption discussed in [1] was correct. Analyzers configurations that use Filters setting incorrect posInc values (e.g. the deprecated PositionFilter) might get incorrect Tagging results. But this is something to be fixed in the configuration and should not border the SolrTextTagger.

* prepared to make skipping of Tokens configurable as discussed in [3] and follow up comments. The Tagger will now log a one time WARNING that tokens where skipped while processing a text and the user should check its analyzer configuration to ensure that skipping tokens is OK. This prepares a new configuration option that will allow users to specify how to deal with skipped tokens.

[1] https://github.com/OpenSextant/SolrTextTagger/pull/11#discussion_r6480063
[2] http://lucene.apache.org/core/4_4_0/analyzers-common/org/apache/lucene/analysis/position/PositionFilter.html
[3] https://github.com/OpenSextant/SolrTextTagger/pull/11#issuecomment-24936225