'ies' finishing verbs' plural form to 'y'

singular verbs like 'flies' or 'tries' were inflected to 'flie' and 'trie' instead of 'fly','try'
Merge branch 'master' of https://github.com/jackred/natural into jackred-master
added unit tests
fixed the singular form inflector for y->ies
Merge branch 'jackred-master'