blis:  New formula

BLIS - BLAS-like Library Instantiation Software

From its own website:  BLIS is a software framework for instantiating
high-performance BLAS-like dense linear algebra libraries.

This commit introduces a formula to build/test/install BLIS.  In most
respects it is very straight-forward, the only non-standard aspect for
which I would especially appreciate some feedback is that BLIS requires
the user specify their desired "framework configuration" to select
compiler options and optimized code for a target platform/architecture.
The formula currently requires a "--with-configuration" option to
specify the framework configuration and raises an error if this option
is not specified.  Thoughts?

Thanks for considering it,
Kevin