Docs Fixes

Mostly basic revisions. Made the "Running Tachyon on a Cluster" section
a more descriptive tutorial on how to do it with spark-ec2.
Add markdown document file for web interface.
Change the title of webInterface.md.
HY's Comments
Merge pull request #112 from manugoyal/docs_revision

Docs Fixes
Merge pull request #114 from grayluck/master

Add markdown document file for web interface.
various doc adjustment