* added block_begin and block_end util to CodeWriter.

* refactored convolution backprop to use block_begin() and block_end()

* relu for interpreter

* relu in serializer

* core fusion

* relu backprop

* relu backprop and test interpreter

* core fusion for CPU

* COREFusion -> CoreFusion

* relu MKL dnn

Merge pull request #493

MKLDNN Emitter

* Add product op

* Add Max (max reduce) and Min (min reduce) ops

* Refactor arithmetic reduction ops to a common base class

* Fix PREFER_EIGEN codepaths in cpu_emitter

* fixed bn weights initialization to correct size

* style fix

mkldnn MaxPoolBprop implementation in CPU emitter

* add mxnet sockeye Seq2Seq model

* update test with sockeye model

unnecessary prefixes can be avoided

- added workaround to attach the maxpool workspace for bprop delta propogation

* change Emit* function to templated