.github: add stale and issue template enforcement

This change will allow probot to enforce our GitHub policies.

.github/ISSUE_TEMPLATE.md

@@ -7,18 +7,26 @@ If you are using a third party client, please create issues on their respective
 Are you using a development build of Clair (e.g. quay.io/coreos/clair-git)?
 Your problem might be solved by switching to a stable release (e.g. quay.io/coreos/clair).
 
+Issues that do not contain the Environment section will be automatically closed.
+If you're making a feature request, please specify "N/A" under the environment section.
+Nobody can help you without context.
+
 -->
 
-**Description of Problem**:
+### Description of Problem / Feature Request
 
+<!--- your content here --->
 
-**Expected Outcome**:
+### Expected Outcome
 
+<!--- your content here --->
 
-**Actual Outcome**:
+### Actual Outcome
 
+<!--- your content here --->
+
+### Environment
 
-**Environment**:
 - Clair version/image: 
 - Clair client name/version: 
 - Host OS: 

.github/issue-close-app.yml

@@ -0,0 +1,4 @@
+comment: "This issue is closed because it does not meet our issue template. Please read it."
+issueConfigs:
+- content:
+  - "### Environment"

.github/stale.yml

@@ -0,0 +1,12 @@
+daysUntilStale: 60
+daysUntilClose: 7
+exemptLabels:
+- lifecycle/preserve
+exemptProjects: true
+exemptMilestones: true
+staleLabel: lifecycle/stale
+markComment: >
+  This issue has been automatically marked as stale because it has not had
+  recent activity. It will be closed if no further activity occurs. Thank you
+  for your contributions.
+limitPerRun: 30