Revised the GitHub issue template

.github/ISSUE_TEMPLATE.md

@@ -1,28 +1,41 @@
 <!--
-    Please note: GitHub issues are to be used only for feature requests
-    and bug reports. For installation assistance or general discussion,
-    please join us on the mailing list:
+    Before opening a new issue, please search through the existing issues to
+    see if your topic has already been addressed. Note that you may need to
+    remove the "is:open" filter from the search bar to include closed issues.
+
+    Check the appropriate type for your issue below by placing an x between the
+    brackets. If none of the below apply, please raise your issue for
+    discussion on our mailing list:
 
         https://groups.google.com/forum/#!forum/netbox-discuss
 
-    Please indicate "bug report" or "feature request" below. Be sure to
-    search the existing set of issues (both open and closed) to see if
-    a similar issue has already been raised.
--->
-### Issue type:
+    Please note that issues which do not fall under any of the below categories
+    will be closed.
+--->
+### Issue type
+[ ] Feature request <!-- Requesting the implementation of a new feature -->
+[ ] Bug report      <!-- Reporting unexpected or erroneous behavior -->
+[ ] Documentation   <!-- Proposing a modification to the documentation -->
 
 <!--
-    If filing a bug, please indicate the version of Python and NetBox
-    you are running. (This is not necessary for feature requests.)
+    Please describe the environment in which you are running NetBox. (Be sure
+    to verify that you are running the latest stable release of NetBox before
+    submitting a bug report.)
 -->
-**Python version:**
-**NetBox version:**
+### Environment
+* Python version:  <!-- Example: 3.5.4 -->
+* NetBox version:  <!-- Example: 2.1.3 -->
 
 <!--
-    If filing a bug, please record the exact steps taken to reproduce
-    the bug and any errors messages that are generated.
+    BUG REPORTS must include:
+        * A list of the steps needed to reproduce the bug
+        * A description of the expected behavior
+        * Any relevant error messages (screenshots may also help)
 
-    If filing a feature request, please precisely describe the data
-    model or workflow you would like to see implemented, and provide a
-    use case.
+    FEATURE REQUESTS must include:
+        * A detailed description of the proposed functionality
+        * A use case for the new feature
+        * A rough description of any necessary changes to the database schema
+        * Any relevant third-party libraries which would be needed
 -->
+### Description