Subject table is simpler, closes #83 and #96.

- Got rid of self-reported mass column and replaced the NA's in the Measured
  Mass column with the self-reported mass. Noted this in the caption of the
  table. issue #83
- Added a mkdir to the subject table so that you can run it first in a fresh
  repo with no issues. issue #96
Merge pull request #103 from csu-hmc/issue-83

Subject table is simpler, closes #83 and #96.