Fix #107 Remove SSHKit::Backend::Printer.invoke, an alias of SSHKit::Backend::Printer.execute and add test.
Remove unnecessary variable declaration in SSHKit::Backend::TestPrinter.test_invoke_raises_no_method_error.
Update Readme to thank all contributions.
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of github.com:capistrano/sshkit
Merge pull request #108 from hab278/master

SSHKit::Backend::Printer.invoke no longer exists.