Merge branch 'add_contributing' into 'master'

Add CONTRIBUTING

See merge request !2

CONTRIBUTING

+CONTRIBUTING
+
+Branches
+
+We maintain master as the production branch and tag it with release names. If you wish to contribute to PubSweet then you need to make a branch and then issue a pull request following this procedure:
+create a user account on Coko GitLab : http://gitlab.coko.foundation
+Clone master with git clone git@gitlab.coko.foundation:pubsweet/pubsweet.git
+Create a new branch and work off that. Please name the branch which sensibly identifies the feature you are working on. You can push the branch to Coko Gitlab at anytime.
+
+Getting your contributions merged
+
+This is a two part process, first ask for comments, then ask for the changes to be merged.
+Ask for feedback generate a Merge Request (Pull Request) from the GitLab interface but do not assign this request to anyone. You do this from the Gitlab
+UI on your branch.
+Look at the feedback and alter your branch as necessary.
+To merge with master - generate a merge request (Pull Request) and assign to Jure Triglav. You do this from the Gitlab UI on your branch.
+We encourage feedback and discussion from as many people as possible on Merge Requests!
+
+Before merging all PRs must fulfill these three simple rules:
+
+1. Before a PR can be merged, it must pass the tests.
+2. Before a PR can be merged, it shouldn't reduce the test coverage.
+3. Bugfixes go in PRs and a bugfix PR shouldn't be merged without a regression test.
+
+Bug reports, feature requests, support questions
+
+This is all done through GitLab using their native issue tracker
+Visit the master issue tracker for PubSweet (https://gitlab.coko.foundation/pubsweet/pubsweet/issues)
+Add an issue
+Tag the issue with 'support', 'bug', or 'feature' to identify the nature of your issue
+
+Releases - follow one simple rule:
+
+1. Tests must pass.