support UBUNTU MIRROR and modify doc

Cmrnorm

Matrix API refactor

Add const in ParameterUpdater init

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

Synchronic code from PaddlePaddle/Paddle

reference or raw matrix (Matrix & or Matrix *)
contextProjectionForward
contextProjectionBackward
contextProjectionBackwardData
contextProjectionBackwardWeight
classificationError
The mul functions would be updated later.

fix typo: you -> we

fix dead links and refine tutorials/index

Fix RNN unittest bugs.

Added support for cudnn v6 and cuda 8.0

Clean BatchNorm Code.

add cluster_train_cn.md

refine data_sources.py and PyDataProvider2.py to make more readable