Removed useless backticks
capitalise Vagrant
Added full stop
Syntax highlight commands in contributing.rst
Syntax highlight a command
Improved indentation
Fixed up some shell prompts
Use double backticks instead of single
Double backticks
Double backticks
Double backticks
Merge pull request #522 from ClusterHQ/minor-typos-etc-11aug

Minor typos and other formatting improvements.

Fixes #522.