* The original SparseRowMatrix use two fields to store each rows,
  which let code very confusing. Try to extract a RowBuffer class,
  for SparseRowMatrix data storage, and manage auto-growth logic.

Remove m4 when generate protobuf

adding input type check for python data provider

* Also fix a protential bug in WarpCTCLayer.cpp

fix some dead links in doc/

Also fix compile issues

add submodule instructions in build_and_install doc

Add inline and bit manipulation in CpuId.h

Feature/travis pre commit checks

Fix bugs in Docker document

Fix Travis-CI when using rebase.

* The $TRAVIS_COMMIT_RANGE could be not existed, because the git history
  can be changed and rebased. Here we alway run Travis-CI when `git diff`
  cannot return the modified files.
* Also do not push docs update if is not PaddlePaddle/Paddle.

Fix dead links in quick start after reorganzing documentaion directory

Bazel protobuf and gtest

Do not use https://github.com/pubref/rules_protobuf, but use https://github.com/google/protobuf/ as external dependency for protobuf

Remove sudo from Dockerfile.*

test code for issue #729

remove breathe and doc/howto/source directory