Add Doxygen support

Add input/output tensor information to nodes.

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

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

update top sort to be linear rather than exponential complexit to b…

All tuples are expanded out to their component tensors.

Output: Describes one tensor output of an node
Input: Described one tensor input to a node, including the output supplying the value.

Finish type propagation in dot, add unit tests

add cmake finder for graphviz dot program and then conditionally comp…

A few binary elementwise ops

fix install directory name. not sure why it worked on osx, but who re…

add cmake finder for graphviz dot program and then conditionally compile visualization based on finding

Finish broadcast type propagation, add tests.

Add eigen support

add eigen as external project.
add very simple eigen unit test to test building/linking

Fix/sanitize type comparisons, add test

* Cleaned up the CMakeLists.txt to properly do the include paths and fixed the install targets.
Also cleaned up the header files located in sub directories.
* Added a simple C++ example with Makefile.
* UPdated the readme with TF usage instructions.

De-use and cleanup op names.

Cyphers/names