Merge pull request #593 from pitr-ch/master

Add ISSUE_TEMPLATE

Author: Petr Chalupa

CONTRIBUTING.md renamed to .github/CONTRIBUTING.md

@@ -0,0 +1,10 @@
+<!-- Thank you for submitting an issue! -->
+
+
+
+<!-- Please fill following if applicable, delete otherwise: -->
+******
+-   Operating system: linux / mac / win
+-   `concurrent-ruby` version: x.y.z
+-   `concurrent-ruby-ext` installed: yes / no
+-   `concurrent-ruby-edge` used: yes / no