Initial commit for Bootstrap layout

A lot to be modified ... = =
Major improvement
Keyboard shortcuts fixed

line 407~421:  keyboard shortcuts fixed
right arrow to the next word
left arrow to show the answer
Minor fixes
New css and several UI improvement
New feature

show answer button: changed to toggle showing and hide
several new logic of element appearance
Minor changes

line 253: 中文->chinese
line 428: add new description
UI changed and new description added

removed the navibar
added the description of the website in the jumbotron area
Merge pull request #1 from kyletsoadl/bootstrap

Bootstrap