add a pull request template (#355)

* add .github/PULL_REQUEST_TEMPLATE.md

* update whatsnew, minor edit template

* friendly pr template

* add description request, delete request

Author: wholmgren

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,17 @@
+pvlib python pull request guidelines
+====================================
+
+Thank you for your contribution to pvlib python!
+
+You may submit a pull request with your code at any stage of completion, however, before the code can be merged the following items must be addressed:
+
+ - [ ] Closes issue #xxxx
+ - [ ] Fully tested. Added and/or modified tests to ensure correct behavior for all reasonable inputs. Tests must pass on the TravisCI and Appveyor testing services.
+ - [ ] Code quality and style is sufficient. Passes ``git diff upstream/master -u -- "*.py" | flake8 --diff`` and/or landscape.io linting service.
+ - [ ] New code is fully documented. Includes sphinx/numpydoc compliant docstrings and comments in the code where necessary.
+ - [ ] Updates entries to `docs/sphinx/source/api.rst` for API changes.
+ - [ ] Adds description and name entries in the appropriate `docs/sphinx/source/whatsnew` file for all changes.
+
+Please don't hesitate to ask for help if you're unsure of how to accomplish any of the above. You may delete all of these instructions except for the list above.
+
+Brief description of the problem and proposed solution (if not already fully described in the issue linked to above):

docs/sphinx/source/whatsnew/v0.5.0.rst

@@ -35,6 +35,7 @@ Documentation
 ~~~~~~~~~~~~~
 * Added ModelChain documentation page
 * Added nbsphinx to documentation build configuration.
+* Added a pull request template file (:issue:`354`)
 
 Testing
 ~~~~~~~