* 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
added an unit test that triggers skipped tokens.
The TaggerRequestHandler now supports a new boolean Request Parameter 'allowSkippedTokens' that can be used to allow skipping of tokens. By default UnsupportedTokenExceptions are thrown if the query time Analyzer emits tokens with 'posInc == 0'.

This also adds three unit tests for testing (1) the default (2) deactivating and (3) activating the feature.

@David: Hope you can come up with a better name for the new request parameter.
Add 'skipAltTokens' (vs error) parameter, renamed from "allowSkippedTokens".

Also, added initialization of top level init args as invariants.