Rewrite github template

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,21 +1,7 @@
 <!--
 
-Thank you very much for contributing to imag.
-
-Please notice: I, the author of imag, am currently on a sabatical (May 2018
-until early 2019). I am not sure whether I will have access to the internet
-during that time. I may respond slowly - delay of 2-4 weeks or even more are
-possible! I hope it won't be more.
-
--->
-
-<!--
-
 IMPORTANT NOTICE
 
-We will close issue and PR contributions via github at some time in the future
-(more information [here](https://imag-pim.org/blog/2018/06/10/off-of-github/))!
-
 Github is only used for CI right now, main development continues on the
 mailinglist.
 
@@ -24,11 +10,3 @@ format-patch` + `git send-email`) to
 [the imag mailinglist](https://imag-pim.org/mailinglist/).
 
 -->
-
-### PR type
-
-- [ ] Bugfix
-- [ ] Feature
-- [ ] Refactor/dependency update
-- [ ] Other
-