Add PR requirements to the docs

[laceysanderson]

This PR adds PR requirements to the docs that are based on Tripal 3 and include the decision by the PMC in Issue #10.
This PR does not close Issue #10.

To Be reviewed by PMC + Tripal community:

Please let me know if you DO or Do NOT agree with the following additions:

• PRs must be left unmerged for 3 weekdays to give core developers a chance to learn from each other and provide any feedback. Larger or particularly important/interesting PRs should be announced in the Slack #core-dev channel.
• PRs must describe what they do and provide manual testing instructions.
• If providing a PR review, please keep the following in mind:
  • Use of deprecated functions should be pointed out but do not block merge.
  • Limit your comments to merge blocking and deprecated functions. Any other concerns you have you can create an issue to document in the repository and assign it to yourself.
  • Concerns are merge blocking if they are examples of these guidelines not being followed (e.g. no automated testing) or if the functionality being added does not work as described or produces a WSOD.

Please check my wording here:

• PRs that include new functionality must also provide Automated Testing.
  • A PR should not reduce the overall test coverage of the repository. Code Climate will comment on your PR with the total coverage in the repository and include the change caused by your PR. This change must not be negative.
• PRs must pass all automated testing marked as "Required" at the bottom of the PR.

And as always, I welcome any + all feedback on these changes

These are the changes in full:

[Ferrisx4]

The three day waiting period will be helpful, I like it. Sometimes it is easy to miss a change that gets merged right away.

[laceysanderson]

I brought this up with @spficklin in the cofest today and this was his feedback:

• we do want deprecated functions to be merge blocking (exception only for PRs relating to functionality for the first alpha).
• the following sentence is confusing and we may want to remove it.

  Limit your comments to merge blocking and deprecated functions. Any other concerns you have you can create an issue to document in the repository and assign it to yourself.

Thanks! I'll make changes accordingly and then re-request review.

[laceysanderson]

Ok, I made the changes Stephen mentioned back in October 🙈 so this can be merged now.