update pull request template

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,13 +1,14 @@
-<!--- Provide a general summary of your changes in the Title above -->
-
 ## Description
 
 <!--- Describe your changes in detail -->
 <!--- Why is this change required? What problem does it solve? -->
 
 ## Related issue
 
-<!--- Please link to the issue here. -->
+<!--- Replace '000' with the issue number. -->
+<!--- Do not include a URL. -->
+
+#000
 
 ## How Has This Been Tested?
 
@@ -19,15 +20,15 @@
 
 ## Types of changes
 
-<!--- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->
+<!--- What types of changes does your code introduce? Put an 'x' in all the boxes that apply: -->
 
 - [ ] Bug fix (non-breaking change which fixes an issue)
 - [ ] New feature (non-breaking change which adds functionality)
 - [ ] Breaking change (fix or feature that would cause existing functionality to change)
 
 ## Checklist:
 
-<!--- Go over all the following points, and put an `x` in all the boxes that apply. -->
+<!--- Go over all the following points, and put an 'x' in all the boxes that apply. -->
 <!--- If you're unsure about any of these, don't hesitate to ask. We're here to help! -->
 
 - [ ] My code follows the code style of this project.