Check to ensure that writeStream exists before writing.
Fixes #62
Merge pull request #63 from adobe-photoshop/jrb/issue-62

Check to ensure that writeStream exists before writing
Fixed a copy & paste error
Add nodeunit
Merge pull request #64 from adobe-photoshop/jrb/nodeunit

Add nodeunit
Add an API to get and set plug-in specific generator settings
Merge pull request #65 from adobe-photoshop/dk/metadata

Add an API to get and set plug-in specific generator settings
Merge branch 'master' into svg/disable