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
Fix for #10
No more napa!
Merge branch 'parser-and-tokenizer' into develop