Update README.md

Corrected spelling of word and eliminated unecessarily repeated word.
Merge pull request #248 from jesuscreyes/cs100-2014fall

Update README.md
Update README.md

Changed "it" to "is" to make better sense of the sentence
Merge pull request #250 from DustinPham/cs100-2014fall

Update README.md
Merge remote-tracking branch 'upstream/cs100-2014fall' into cs100-2014fall