Added a PR template to hopefully simplify the review process

.github/PULL_REQUEST_TEMPLATE.md

+Please provide the following information:
+
+ - Link to your code repository:
+ - Link to the tags page with at least one [semver](http://semver.org) tag: 
+
+Also make sure you:
+
+ 1. Used `"tags": true` and not `"branch": "master"` ([versioning docs](https://packagecontrol.io/docs/submitting_a_package#Step_4))
+ 2. Ran the tests ([tests docs](https://packagecontrol.io/docs/submitting_a_package#Step_7))