v0.1.0: initial tsunami release

This initial release provides D bindings for the core MXNet C API and a friendly D wrapper library for the following key functionality:

• symbolic logic (the Symbol class and its subclasses)

• imperative operations on n-dimensional arrays (NDArray)

• an Executor class to bind NDArray inputs and outputs to
  symbolic expressions

Other parts of the wrapper code provide internal support for lower level interactions with the underlying C API, such as handles, atomic symbols, CPU/GPU contexts, and convenience wrappers for invoking API functions.

Some basic integration sanity checks are provided by a test suite that performs multi-class logistic regression on the MNIST dataset.