Fixed a bunch of typos

(cherry picked from commit b7cd62fbda05147e132e1fdc5528304e17e262bf)
Added package gokogiri to the dependency list on README

(cherry picked from commit 03b63e08a0cac560ab203715158f61590d244c1e)
Added reference to API docs in README

(cherry picked from commit 62a0edfeb2c88dd659e5b467b511bbbff20184a7)