allowing for 0 parameter in levenshtein distance
added length condition for verbs stem

short verbs like 'is', 'are' or 'has' got stemmed in the form of 'i', 'ar' and 'ha' which is incorrect.
added condition to exclude verbs of 3 characters or less from stemming
Merge pull request #108 from jackred/master

added length condition for verbs stem
Merge pull request #105 from dsullivan7/levdist

allowing for 0 parameter in levenshtein distance
ticked 0.1.25
corrected some plural forms

support for tornadoes, ephemerides and cortices nouns
updated unit tests
Merge branch 'master' of https://github.com/NaturalNode/natural
Merge branch 'master' of https://github.com/NaturalNode/natural into english_normalizer