* Make this demo support GPU

* hidden decorator kwargs in DataProvider.__init__
* also add unit test for this.

* hidden decorator kwargs in DataProvider.__init__
* also add unit test for this.

* hidden decorator kwargs in DataProvider.__init__
* also add unit test for this.

Add excluded_chunk_types to ChunkEvaluator

The chunks of types in excluded_chunk_types will not be counted in
ChunkEvaluator. This is useful for tasks such as SRL, in which chunks of
type V (verb) will not be taken into account in evaluation.

Add unittest to cover SgdThreadUpdater's enableBufType

fix typo: you -> we

fix dead links and refine tutorials/index

Fix RNN unittest bugs.

Added support for cudnn v6 and cuda 8.0