Added readme file.

README.md

+Build Status - master (This is stable branch): [![Build Status - master](https://travis-ci.org/BhallaLab/moose.svg?branch=master)](https://travis-ci.org/BhallaLab/moose)
+
+This is a meta repository of MOOSE simulator. It contains MOOSE, its GUI and
+other sister projects a submodule. For more details about these projects, read
+respective README files.
+
+# Install 
+