Update PULL_REQUEST_TEMPLATE.md

Improved text

.github/PULL_REQUEST_TEMPLATE.md

+##### Description
+
+<!-- describe here your pull request -->
+
+##### Target release
+
+<!-- please tell us where you would like your code to appear (e.g. v2.4): -->
+I would like my code to appear in release __XXXXX__
+
+##### Type of contribution
+
+<!--
+  Please select the type of your contribution among these:
+  (Change [ ] to [X] to tick an option)
+-->
+- [ ] changes to code or doc authored by PLUMED developers
+- [ ] changes to a module not authored by you
+- [ ] new module contribution or edit of a module authored by you
+
+##### Copyright
+
+<!--
+  In case you picked one of the first two choices
+  MAKE SURE TO TICK ALSO THE FOLLOWING BOX
+-->
+
+- [ ] I agree to transfer the copyright of the code I have written to the PLUMED developers or to the author of the code I am modifying.
+
+##### Tests
+
 Make sure these boxes are checked before submitting your pull request:
 
 - [ ] I added a new regtest or modified an existing regtest to validate my changes.
-- [ ] I verified that all regtests are passed successfully on Travis.
-- [ ] I agree to transfer the copyright of the code I have written to the PLUMED developers.
+- [ ] I verified that all regtests are passed successfully on Travis-CI.