Added sharelatex cloud compiler badge

Author: jsimnz

README.md

@@ -1,2 +1,4 @@
-specification
+Hermes Specification (Whitepaper)
 =============
+
+[![PDF Status](https://www.sharelatex.com/github/repos/Hermes/specification/builds/latest/badge.svg)](https://www.sharelatex.com/github/repos/Hermes/specification/builds/latest/output.pdf)