Added support for DiffMerge on Mac
Automatically configures git to use DiffMerge by default, but can be disabled with attributes
Change use of 'node' configuration to avoid Chef warning
Added checksum for diff_merge recipe
Fixed file ownership problem for .gitconfig file by setting 'user' to 'WS_USER' for command execution
Merge pull request #202 from webcoyote/pivotal-diffmerge

Added support for DiffMerge on Mac