ResourseConverters: Promising, Asynchronous, Pluggable & Reusable

ResourceConverters:

• fix #30 - Both Synchronous & Asynchronous (nodejs callbacks & A+ promises) ResourceConverters
• fix #58 - RC's have options :

a) When creating using the alternative array [] format its the *last item, or it can take the place of convFilename if that is misisng.

b) When searching, a ['rcname', {some: 'option'}] style lookup can be used that updates options. It allows a changed filez shortcut like ['less', ['myStyle/**/*.less'], { $srcMain: 'style/myMainStyle.less'} ]

• fix #57 - loading RCs from node_modules/urequire-rc-#{rcname} if not already on registry.
• RC properties passed along with options: {$: {srcMain:'...', convertFilename: '...'}} or options: { $srcMain: '...', $convertFilename: '...' }
• If the same RC appears in bundle.resources more than once, only the last declared one remains. Effectively you change its position. If you really want them twice, clone 'em :-)
• All FileResource <-- TextResource <-- Module instances now have a srcMainFilepath & srcMainRealpath property.
• Bug fixed when instantiated and registered a new ResourceConverter

config:
build.deleteErrored (cleans dst file while src is in error)

Internal / refactoring:
Bundle:

• Many methods now return when/A+ promises
• Minimized usage of when.promise(resolve, reject) - when.node.lift is much better.
• getBundleFile method
• srcMain handling / throwing if not in @filenames
• better duplicate src error handling (but still jerky on watch)
• clean dst when source is missing
• improved bundle.printError

Module.convert(@build)

urequire-spec:

• cloning & copying ../urequire_example to temp/urequire_example