add issue template and link to CONTRIBUTING.md in README (#1003)

Author: bshaffer

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,8 @@
+**Heads up!**
+
+We appreciate any bug reports or other contributions, but please note that this issue
+tracker is only for this client library. We do not maintain the APIs that this client
+library talks to. If you have an issue or questions with how to use a particular API,
+you may be better off posting on Stackoverflow under the `google-api` tag.
+
+Thank you!

README.md

@@ -304,6 +304,10 @@ One additional step is required in Charles to view SSL requests. Go to **Charles
 
 YouTube: https://github.com/youtube/api-samples/tree/master/php
 
+## How Do I Contribute? ##
+
+Please see the [contributing](CONTRIBUTING.md) page for more information. In particular, we love pull requests - but please make sure to sign the [contributor license agreement](https://developers.google.com/api-client-library/php/contribute).
+
 ## Frequently Asked Questions ##
 
 ### What do I do if something isn't working? ###
@@ -312,10 +316,6 @@ For support with the library the best place to ask is via the google-api-php-cli
 
 If there is a specific bug with the library, please [file a issue](/Google/google-api-php-client/issues) in the Github issues tracker, including an example of the failing code and any specific errors retrieved. Feature requests can also be filed, as long as they are core library requests, and not-API specific: for those, refer to the documentation for the individual APIs for the best place to file requests. Please try to provide a clear statement of the problem that the feature would address.
 
-### How do I contribute? ###
-
-We accept contributions via Github Pull Requests, but all contributors need to be covered by the standard Google Contributor License Agreement. You can find links, and more instructions, in the documentation: https://developers.google.com/api-client-library/php/contribute
-
 ### I want an example of X! ###
 
 If X is a feature of the library, file away! If X is an example of using a specific service, the best place to go is to the teams for those specific APIs - our preference is to link to their examples rather than add them to the library, as they can then pin to specific versions of the library. If you have any examples for other APIs, let us know and we will happily add a link to the README above!