Update PULL_REQUEST_TEMPLATE.md

Author: woodthom2

.github/PULL_REQUEST_TEMPLATE.md

@@ -28,6 +28,7 @@ Please describe the tests that you ran to verify your changes. Provide instructi
 
 ## Checklist
 
+- [ ] My PR is for one issue, rather than for multiple unrelated fixes.
 - [ ] My code follows the style guidelines of this project.  I have applied a Linter (recommended: Pycharm's code formatter) to make my whitespace consistent with the rest of the project.
 - [ ] I have performed a self-review of my own code
 - [ ] I have commented my code, particularly in hard-to-understand areas