Fixed some typos and grammatical errors

Fixed some typos and grammatical errors
corrected typos and grammar 

spotted by @risdenk
corrected typos and grammar 

spotted by @risdenk
Corrected some typos and grammar

Corrected some typos and grammar
Merge branch 'master' of github.com:vivganes/hadoop-tutorials
Merge pull request #26 from vivganes/master

Fixed some typos and grammatical errors