`lsstsw` & `newinstall.sh` pinned conda package versions

There was a bit too much excitement this past week with the conda release of MKL dependent packages breaking the build (see: DM-5105). Reproducible builds have been an on going intermittent problem and this was only the latest example. We have been hesitant to over aggressively control the python dependencies for fear of encouraging brittle software. As an intermediate position, lsstsw/bin/deploy and newinstall.sh now pin their conda package versions to this file: conda_packages.txt. SQRE has committed to updating the conda package list on an approximately monthly basis.

There is a new -b (for bleed) flag to deploy that disables the pinned package versions.

Usage: ./deploy [-b] [-h]

Specifc options:
   -b          use bleeding edge conda packages
   -h          show this message

The travis configuration for lsstsw now runs the deploy script both with and without the -b flag and diffs the installed package set vs. conda_packages.txt. Here is an example of the CI output when no upgraded conda packages are available: https://travis-ci.org/lsst/lsstsw/jobs/108814815#L1573-L1574