Added options for exec command and a new exec_all command.
Merge pull request #105 from JCook21/ExecCommands

Further work on exec command
Added documentation for the exec and exec_all commands.
Merge pull request #101 from nicolasmccurdy/use-libraries

Use stdlib methods to replace most non-git shell calls. Looks good.
Add a Gitter badge to the readme
Start using rugged for commands that don't need to show git output
Use Rugged instead of the ` syntax for shell calls
Use rugged instead of system in the spec helper