Add .gitignore to lib directory
Add .gitignore to lib directory

dpvc/MathJax-dev,Khan/MathJax-dev,Khan/MathJax-dev,Khan/MathJax-dev,Khan/MathJax-dev,Khan/MathJax-dev,dpvc/MathJax-dev,dpvc/MathJax-dev,Khan/MathJax-dev,dpvc/MathJax-dev,dpvc/MathJax-dev,dpvc/MathJax-dev