Code cleanup and comment updates
Handle image views that aren't targets in cancel
Allow ModelLoaders to return null values

This allows models to sometimes, but not always,
have an associated image. If a ModelLoader returns
null, we will assume there is no image associated
with that particular model instance and show
the placeholder.
Make buildModelLoader a static method on Glide

It's not a setter, so it might as well have the
slightly simpler static syntax.
Add version name to Glide jars in ant
Best effort attempt to avoid memory leaks

The ImageManager will only retain weak references
to the various loaders/transformations/ etc so 
that if they do have a reference to a context
Glide will not cause a memory leak. The only class
this is imperfect for is StreamLoader which is 
likely to be referenced by some callback passed
in to another library, hence the warning note.
Remove some overly verbose log lines
update readme
rebuild before making jars
Bump version to 2.0.0