susQuad function take sus Struct instead of full ifo

create cleaner module for physical constants, and use everywhere.

This reverts commit 4a60fc58.

This was not an appropriate fix to whatever was needing to be addressed.

matplotlib: use hex color names instead of the cool xkcd ones
When matplotlib >= 2.0 is ubiquitous, we can revert this.
numpy: use np.flipud in place of np.flip
np.flip only exists in numpy >= 1.12, and flipud is clearer anyway.

Suspension type BQuad changes the bottom stage material to silicon.
Reverse the SUS stage list in suspensionthermal.py to use the appropriate Temp.
Addresses #23

This is a rote copy of the new suspQuad code in matgwinc that iterates over
the stages, and supports tapered fibers:

https://git.ligo.org/gwinc/matgwinc/commit/a59f01192a1ffc1644a45be536e31bc0eb78bd7c#9cb6e594e14c1d61dbb3c91549166a2d48db194f

This allows for setting per-stage temperature and wire and blade properties.

This version differs slightly in some generalizations about the number of
stages, although it doesn't quite yet support an arbitrary numer.

Improves readbility.  use translation for MATLAB purposes.

These two functions were basically identical except for the material
used for the test mass stage, and a hacky reduction of the spring
constant for silicon.

suspQuad is modified to support different materials for the test mass
stage, and a hacky switch is added to adjust the spring constant.
suspBQuad is now just a wrapper around suspQuad specifying that the
test mass material is silicon instead of silica (there is definitely a
better way to do this, by e.g. specifying the fiber material in the
Stages struct list).

don't need to be defined inside of the suspQuad function

move this out of noise package, since it's not actually directly a noise
calculation.  no functional change.

ifo.Suspension.Type now accepts string for suspension calc func, e.g. 'Quad'
for 'suspQuad' calc.

This is now commensurate with what matlab gwinc does, and makes the IFO
structures directly comparable without any hacky conversions.

no functional change

Reproduces the Voyager noise curves but still needs testing with other IFO models.