Chaining related changes

Also minor bug fix in rule test
Updated javadoc for missed case
Filter rule tests

TokenFilter tests for all except stemmer. Modified requirements to
capture chaining requirements
(Porter) Stemmer test
Tokenzier tests
TokenStream tests
Token tests
Indexer tests + bug fixes
Teeny-tiny fix
Minor fixes
Remember to save before commit :P
0 shouldn't be in index
Fixed #8
Merge pull request #1 from nicklondhe/master

updates