Dependency updates.
Handle nulls correctly for all parameters.

Closes #210.
Merge pull request #214 from square/jw/nulls

Handle nulls correctly for all parameters.
Merge pull request #216 from square/jw/gson-update

Dependency updates.
Allow uppercase letters in path parameters.
Merge pull request #218 from square/jw/earl

Allow uppercase letters in path parameters.
Prepare version 1.0.2.
[maven-release-plugin] prepare release parent-1.0.2
[maven-release-plugin] prepare for next development iteration
Add hook for customizing exceptions

The exceptions can be customized via a new ErrorHandler class, which is
responsible for returning customized exceptions during synchronous
requests.
Forbid returning null from error handler.

A bunch of code style and test clean-up as well.
Code style cleanup.
Be null.
Rename samples/ to retrofit-samples/

Also move it to its own groupId.