Add issue templates

Trying to discourage people from opening issues that are completely unrelated to the hub project

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,17 @@
+---
+name: Bug report
+about: Unexpected or broken behavior of "hub" command-line tool
+title: ''
+labels: bug
+assignees: ''
+
+---
+
+**Command attempted:**
+<!-- e.g. `hub pull-request --head mybranch` -->
+
+**What happened:**
+<!-- describe the faulty behavior you've been experiencing -->
+
+**More info:**
+<!-- output of `hub version`, your OS version, steps to reproduce, etc. -->

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,14 @@
+---
+name: Feature request
+about: Suggest new functionality for "hub" command-line tool
+title: ''
+labels: feature
+assignees: ''
+
+---
+
+**The problem I'm trying to solve:**
+<!-- describe the problem that you think hub might help you with -->
+
+**How I imagine hub could expose this functionality:**
+<!-- e.g. `hub my-new-command --some-flags` -->