Fixed GenFSM example code and typos.
Updated GenFSM example code
Wrap Mix.Shell.cmd with " instead of '

Single quotes can't be escaped in the shell so commands containing '
will not work. Instead wrap the command in double quotes that can be
escaped and escape " in the command.
Merge pull request #1478 from ericmj/mix-cmd-quotes

Wrap Mix.Shell.cmd with " instead of '
Merge pull request #1477 from jwarwick/genfsm_docs

Updated GenFSM