Updates docs to make it clear the Chunker training format
Updates docs to make it clear the Chunker training format

The documentation was not clear, leading the user to think that any number of spaces could be used as column separator. This updates the documentation stating that only single space is acceptable.

Closes OPENNLP-743
Closes apache/opennlp#25

ragerri/opennlp,jzonthemtn/opennlp,ragerri/opennlp,apache/opennlp,ragerri/opennlp,apache/opennlp,jzonthemtn/opennlp,apache/opennlp,jzonthemtn/opennlp