Allow csshX to respect identity_file
Use FFI binders to attach :SendMessageTimeout instead of Win32API in order to disable annoying message of:

DL is deprecated, please use Fiddle
include module on windows only
Bump ffi version since chef-dk depends on chef and dep-selector and dep-selector uses ~> 1.9.
Use FFI::LastError instead of GetLastError for ffi 1.9.x compatibility.
Fix windows specs.
Misc spec fixes for windows.
Merge pull request #1528 from opscode/sersut/bump-ffi-version

Bump ffi version since chef-dk depends on chef and dep-selector and dep-selector uses ~> 1.9.
Update for new FFI binding.
Merge pull request #1525 from opscode/mcquin/chefdk-69

Use FFI binders to attach :SendMessageTimeout instead of Win32API.
Remove confusing gemspec comment about the no-longer-used json gem
Merge pull request #1547 from juliandunn/confusing-json-comment

Remove confusing gemspec comment about the no-longer-used json gem
Merge pull request #1520 from curiositycasualty/knife-ssh-identity-file

Allow cssh(X) to respect identity_file