Standard release process

[j-wags]

Based on https://github.com/openforcefield/openforcefield/issues/286

This is something like a pre-flight checklist to make sure we don't make unnecessary errors in the process of releasing new FFs.

1: Prepare changes in a PR

• Open a new branch or fork on this repo.
• Add the new force field file to the branch.
• Draft a "version" description at the bottom of the README file in a branch or fork. A zenodo DOI link is not necessary at this stage
• Open a PR to master

2: Get PR approved by at least one repo maintainer

3: Cut an official release, following this template:

Tag = X.Y.Z @ master

Title = Version X.Y.Z

In our paper about the SMIRNOFF format, we introduced a non-zero hydrogen parameter for polar hydrogens. Unfortunately, in the first introduction of these terms in our official force field the rmin_half and epsilon parameters were reversed. Here, we fix that small human error. 

This release also includes a fix for bond parameters between hydrogen and divalent carbons (issue #81) and fixed SMIRKS patterns for angle parameters around trivalent carbon in 5-membered rings (issue #84).

4: Edit the README page to add the most recent Zenodo badge by copying the version-specific badge from here. Information needs to be added in two places:

• The badge needs to be added to a new row in the "filename -> DOI" table in the README
• The "Versions" text at the bottom of the README should be update with the doi.org link for the version release.

5: Trigger build of the new release on Omnia

• Create branch or fork of omnia-md/conda-recipes with changes to smirnoff99Frosst in meta.yaml:
  • version set to match git release
  • tag set to match git release
  • build set to 0
  • any updated dependencies reflected under requirements:
  • If we want to push to special beta label: use extra.upload
• Open PR to merge branch or fork into omnia-md master
  • PR should be called, eg [smirnoff99Frosst] 1.0.10
  • No PR body text is needed
  • PR is then reviewed and merged by omnia maintainers
  • Package is pushed to beta label if upload: beta is set in extras:
  • If we have upload: beta, we would install with conda install -c omnia/label/beta openforcefield
• Test omnia package

6: Announce the release!