mu T calculator (UC1)

[yucongalicechen]

Problem

UC1:

1. user places sample on diffractometer
2. diffractometer determines weight and dimensions of the sample
3. diffractometer shares this information with diffpy.utils
4. diffpy.utils computes muD

(See more discussions in #45)

Proposed solution

[sbillinge]

This is not a diffpy.utils UC. Not sure where to put it but probably labpdfproc?

[yucongalicechen]

moved this to diffpy/diffpy.labpdfproc#144