* Add C++ and python style check to travis.  
* Update all C++/python code that violate coding standards.

Fix some typos

* init paddle

* add image writer

* change sample numble to 4

* add image and conv image

* add histogram

* rename test file

* link in eigen3 library to vl_test target
* Add new "template class SimpleWriteSyncGuard<Entry<long long>>;", since build will fail on OSX
* Add template keyboard to data<T>(0).Get() (otherwise this fails on OSX)
* Fix unit test in sdk_test.cc

Tested build and unit test run on OSX and Ubuntu with no issues

just a trick to store int8 in protobuf

should limit the maximum image shape latter