added minor changes doc; update PR template

Author: wknoben

.github/PULL_REQUEST_TEMPLATE.md

@@ -5,4 +5,4 @@ Make sure all the relevant boxes are checked (and only check the box if you actu
 - [ ] New tests added (describe which tests were performed to test the changes)
 - [ ] Science test figures (add figures to PR comment and describe the tests)
 - [ ] Checked that the new code conforms to the [SUMMA coding conventions](https://github.com/NCAR/summa/blob/master/docs/howto/summa_coding_conventions.md)
-- [ ] Describe the change in the release notes (found here: `./summa/docs/whats-new.md`)
+- [ ] Describe the change in the release notes (use either `./summa/docs/whats-new.md` or `./summa/docs/minor-changes.md` depending on what changed)

docs/minor-changes.md

@@ -0,0 +1,14 @@
+# Minor changes
+
+This page provides simple, high-level documentation about what has changed in each new release of SUMMA.
+
+Documented here are minor changes that do not affect science outputs or are likely to affect only a minority of users:
+- Minor bugfixes
+- Correction of misspellings
+- Changes to formatting
+- Addition of print statements
+- Etc. 
+
+## Version 3.0.4 (pre-release)
+
+- [placeholder]

docs/whats-new.md

@@ -2,6 +2,13 @@
 
 This page provides simple, high-level documentation about what has changed in each new release of SUMMA.
 
+Documented here are large changes that will likely affect the majority of users:
+- New features
+- Changes to the functionality of the code
+- Changes to default settings
+- Changes in code conventions (e.g. variable renaming)
+- Etc.
+
 ## Version 3.0.4 (pre-release)
 
 - Initial addition of the "What's new" page