Issue/PR templates (#180)

* create .github directory to hold issue/PR templates and contributing guide

* update link to Contributing guide in Readme
diff --git a/.github/ISSUE_TEMPLATE b/.github/ISSUE_TEMPLATE
new file mode 100644
index 0000000..1451b81
--- /dev/null
+++ b/.github/ISSUE_TEMPLATE
@@ -0,0 +1 @@
+Before starting a PR, please read the [style guide](https://github.com/gophercloud/gophercloud/blob/master/STYLEGUIDE.md).