adding the historical reference code gepore.f, as published in Chatterji (Neutron Scattering in Magnetic Materials, 2006)
support magnetic incident and substrate media
empty string list in extra compile args breaks compiler
Use is/is not None to check for None; numpy is changing == None to a per-element test
Merge branch 'master' of github.com:reflectometry/refl1d
link reflmodule as c++ on os x
delay load reflmodule so doc build doesn't require compiler
remove debug noise
update installation docs
doc twiddle
doc link fixup; use TeX markup for polymer math
release R0.7.7
doc tweaks
document release process (such as it is)
Optimize slab building for large microslab layers

No need to do all that work when blending is a null op
Slab building optimization is now pure numpy

18x speedup over unoptimized case, 1.7x speedup over the earlier
optimization. (When profiling using examples/polymer/tethered.py with
step_interfaces=True)