Update PR template (ufs-community#813)

Update the 'tests conducted' portion of the template to include a
checklist of required tests before merging.

Fixes ufs-community#811.

.github/PULL_REQUEST_TEMPLATE

@@ -8,13 +8,21 @@
 
 - Use the "Preview" tab to see what your PR will look like when you hit "Create pull request"
 
-# --- Delete this line and those above before hitting "Create pull request" ---
+## --- Delete this line and those above before hitting "Create pull request" ---
 
 ## DESCRIPTION OF CHANGES: 
 One or more paragraphs describing the problem, solution, and required changes.
 
 ## TESTS CONDUCTED: 
-State whether the contingency tests were run or are pending, and if they were already run, state the result.  If contingency test baselines need to be updated as a result of this PR, please specify the machine(s) and path(s) to the new files.  Note that running the contigency tests is required for every PR and should be run at least once after all commits or changes have been made after review of the PR.  Make note of the compilers used, the platform/machine, and other relevant details as necessary.  Please also note whether new unit tests or updates to existing ones were required and their file names.
+If there are changes to the build or source code, the tests below must be conducted. Contact a repository manager if you need assistance.
+
+- [ ] Compile branch on all Tier 1 machines using Intel (Orion, Jet, Hera and WCOSS2).
+- [ ] Compile branch on Hera using GNU.
+- [ ] Compile branch in 'Debug' mode on WCOSS2.
+- [ ] Run unit tests locally on any Tier 1 machine.
+- [ ] Run relevant consistency tests locally on all Tier 1 machine.
+
+Describe any additional tests performed.
 
 ## DEPENDENCIES:
 Add any links to pending PRs that are required prior to merging this PR. For example: