desiconda updates for the 18.7 software release

[sbailey]

This PR includes changes for the 18.7 software release:

• astropy 2
• pins matplotlib version due to incompatibility with basemap
• adds ipywidgets and bokeh for spectral viewer
• adds line_profiler (via pip install)
• updates to astrometry.net/0.74 and tractor/dr7.0 (for imaging)

These are installed and tested as desiconda 20180709-1.2.6-spec on cori and edison. After this is merged I'll make the 1.2.6 tag.

[tskisner]

Thanks for this!

[weaverba137]

I thought we were still calling this release 18.6?