Adds Github issue and pull request templates (#242)

* Adds Github issue and pull request templates

  We might need to add few labels for knative/client repo as mentioned
  in the template.

* Adds nightly build reference and swap client and serving section

* Asks user to paste output of kn version in bug report template

.github/ISSUE_TEMPLATE/ask-question.md

@@ -0,0 +1,23 @@
+---
+name: Question
+about: Ask a question about knative/client
+title: ''
+labels: kind/question
+assignees: ''
+
+---
+<!-- If you need to report a security issue with Knative, send an email to knative-security@googlegroups.com. -->
+## In what area(s)?
+
+<!-- Remove the '> ' to select -->
+
+<!--
+Classifications:
+> /kind good-first-issue
+> /kind usage
+> /kind compatibility
+> /kind doc
+-->
+
+## Ask your question here:
+

.github/ISSUE_TEMPLATE/bug-report.md

@@ -0,0 +1,44 @@
+---
+name: Bug report
+about: Report a bug in knative/client
+title: ''
+labels: kind/bug
+assignees: ''
+
+---
+<!-- If you need to report a security issue with Knative, send an email to knative-security@googlegroups.com. -->
+## In what area(s)?
+
+<!-- Remove the '> ' to select -->
+
+<!--
+Classifications:
+> /kind good-first-issue
+> /kind doc
+> /kind cleanup
+-->
+
+## What version of Knative Client?
+
+> Paste output of 'kn version'
+
+## What version of Knative Serving running on your cluster?
+
+> 0.5.x
+> 0.6.x
+> 0.7.x
+> 0.8.x
+
+## Expected Behavior
+
+<!-- Briefly describe what you expect to happen -->
+
+
+## Actual Behavior
+
+<!-- Briefly describe what is actually happening -->
+
+
+## Steps to Reproduce the Problem
+
+<!-- How can a maintainer reproduce this issue (be detailed) -->

.github/ISSUE_TEMPLATE/feature-request.md

@@ -0,0 +1,24 @@
+---
+name: Feature Request
+about: Create a feature request for knative/client
+title: ''
+labels: kind/feature
+assignees: ''
+
+---
+<!-- If you need to report a security issue with Knative, send an email to knative-security@googlegroups.com. -->
+## In what area(s)?
+
+<!-- Remove the '> ' to select -->
+
+<!--
+Classifications:
+> /kind good-first-issue
+> /kind feature
+> /kind proposal
+> /kind doc
+> /kind cleanup
+-->
+
+## Describe the feature:
+

.github/pull-request-template.md

@@ -0,0 +1,23 @@
+<!--
+Request Prow to automatically lint any go code in this PR:
+
+/lint
+-->
+
+Fixes #
+
+## Proposed Changes
+
+*
+*
+*
+
+**Release Note**
+
+<!-- Enter your extended release note in the below block. If the PR requires
+additional action from users switching to the new release, include the string
+"action required". If no release note is required, write "NONE". -->
+
+```release-note
+
+```