Added UpSampling module and associated tests.

[mikepound]

From issue #1262, a more generic UpSampling module that provides a wrapper to the recently added volumetric upsampling code. Behaves similarly to the pytorch upsample class, in that it infers 2D or 3D upsampling based on the input size, and can operate in either nearest neighbor or linear mode.

• This module is a little thematically different to the existing upsampling modules, in that it works on either spatial or volumetric depending on the input.
• There is cunn testing code, but I didn't include it as this is an nn commit. I wasn't sure if I could push to two repos at once.

[soumith]

thanks Mike!