remove class Op and merge functionality with Node

Function execution

CMake: Replace a previously missed instance of 'git am'

CMake: Use 'patch' instead of 'git am'

Git invocations without an available gitconfig (ex. a test environment)
will fail whereas patch should always work. This adds a build dependecy on patch.

fix namespace collision in runtime test

VM for interpreting ops

* Implemented binops/unops with different return type from args

* Implemented generic bases class for comparison and arith ops, changed current comparison ops to subclass it

* Added a TraitedType for booleans

* Moved arith and comparison ops to separate header files from `op.h`

Change Input/Output to instances in node rather than shared_ptr

CMake: Ninja fixes and MKLDNN integration

Add mechanism for pass dependency checking

Tensors with eigen implementations for addition, multiplication

Start of external function calling support

Add memory layout and liveness passes.

* Fixed the paths in the include statements

* absolute path include, relative to /src

* fix invalid use of incomplete type

* Fixed a compilation error.

Add pass manager

Currently MKL-DNN isn't supported on this platform

Add Doxygen support

add test framework

stuff wired up

benchmark segfault for 5M nodes. fun

make traverse_nodes not recursive

print timings on benchmark

unit test for pass manager

Add input/output tensor information to nodes.

This is temporary and will be removed once upstreamed

Add support for 0D tensors to dot, clean up comments

* Adds a "make doc" command, outputting documentation in
  $BUILD_DIR/doc