missing include

fixing vector length

format fixes

avoid repeating input values in a test

use input

trig/hyper funcs

* Formatting; fix erroneous "type_prop" classification for reduce and slice tests

* Clarify comment

* Add step parameter to slice, with type checking but not (yet) implementation in VM

* Add elementwise exp to VM

* Formatting

* Type checking for reshape op

* Formatting

* Implement reduce op for matrices and smaller in VM

* Formatting

* Missing include for Ubuntu

* Remove IndexBuiltin class

Add a minimal Backend API and make the interpreter use it.
read/write tensors (for frameworks)

* cleanup

* fix node includes

* isolate graph building / execution scope in some unit tests (this triggered the user-after-free which was also observed from TF)

* Change descriptor::layout::TensorViewLayout to store a shared pointer to the TensorViewType rather than a reference to the TensorView

* port functions from funky passman branch

* update pass tests

* wip

* fixed

* remove obsolete test

* remove debug prints

* Type propagation for convert

* Implement "convert" through VM

* Temporary commit to unconfuse git merge

* Undo temporary commit to unconfuse git merge

* Add support for some polymorphic operators (arithmetic, etc.)

* Extend to all other ops except Tuple, which is tricky (not quite sure where to get the needed type info)

* Some tidying(???) up

* Extend to handle Tuple op

* Slightly more descriptive macro name

* Implement broadcasting of scalars through VM

* Implement vector-to-matrix broadcasting through VM

* Add missing files

* Address review comments

Remove old {get,set}_{array_matrix}{_2d,} methods; update dot product to use new Eigen wrapper (#158)

* Have abs use layout.

* Use layout to get vector info

* Add format selector for mapped arrays
Convert some ops
Drop runtime.cpp since we don't expose the functions any more.

* Add vector concat

* concat matrix

* Switch more ops to simpler eigen wrapping

* Add reduce op class and type propagation

* Implement FunctionCall through VM

* Changes Function to require explicit return type at construction time

* cleanup pass registration code.

* Replace explicit code to do passes with pass_manager passes

* make external function work with const types internally, it should not change the graph

* Basic layouts, tuples

* Review comments.

* Add incude for size_t.

* Bop use-after-free in GetTupleElement

* Inline call to get_element_types()

* Implement vector and matrix concatenation through VM

* Address PR comments

* Comments on Concat semantics

* Remove some redundant template parameters in concat_matrix and concat_vector

* Formatting fixes in external_function.cpp

* Vector dot product implementation

* Implement matrix mult instruction in VM

* Add implementations for scalar-tensor and matrix/vector products.

* This is kind of a cheap hack for the moment, at least in the tensor
  constant case: each constant instruction carries around its value,
  and copies that to the result buffer everytime we need it. Ultimately
  we will probably want a pass that allocates space in the call frame
  for constants, similar to what we do for parameters.

* Add elementwise ops to runtime

* equals operator implementation at graph and runtime level

* "Select" operator (elementwise ?:) at graph and runtime level

* A few file renames (`notequal` -> `not_equal`, `lessthan` -> `less_than`)

* Macro wrapping boilerplate for op registration in `external_function.cpp`
  (this covers everything except `op::Parameter`).