Just a quick spell fix

envivonment_string to environment_string
Add parentheses over nohup command
Add test for backgrounding a task with working directory
Add open3 JRuby bugs workaround
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'
Creating the SimpleText formatter per discussion in ticket #120
allow verbosity control in capture
Merge pull request #128 from mhfs/capture_verbosity

Allow verbosity control in capture
Merge pull request #127 from townsen/master

on() should not execute block when no hosts given
Merge branch 'master' of github.com:capistrano/sshkit
Merge pull request #108 from hab278/master

SSHKit::Backend::Printer.invoke no longer exists.
Merge pull request #120 from DejaAugustine/master

Text-only formatter option
Merge pull request #92 from signedbyte/patch-1

Just a quick spell fix
Merge pull request #103 from icmpecho/master

Add parentheses over nohup background command
Merge pull request #104 from SPBTV/fix-jruby

Add open3 JRuby bugs workaround
Raise minimum Net::SSH version requirement
Preparing Release v1.4.0
Fix typo