v0.5.0

• This release brings some new functionality but also contains some breaking changes.
• Added .key to every record bound via bindAsArray() or bindAsObject() which contains the key of the data's corresponding node in the Firebase database.
• Improved performance of bindAsArray(), especially with large data sets.
• Upgraded Firebase dependency to 2.2.x.
• Upgraded React dependency to 0.13.x.
• Primitive values are now stored in an object containing .key and .value instead of as the primitive value itself.
• Attempting to bind to a bind variable which is already bound to a Firebase reference now throws an error. You should call unbind() before re-binding.
• bindAsArray() now properly handles all types of Firebase queries, including limit and order by queries.