Update issue and pull request templates

Author: samtstern

ISSUE_TEMPLATE.md

@@ -1,3 +1,8 @@
+Welcome to FirebaseUI and thanks for submitting an issue!
+
+Please take a look at [open issues](https://github.com/firebase/FirebaseUI-Android/issues?q=is%3Aopen+is%3Aissue), as well as [resolved issues](https://github.com/firebase/FirebaseUI-Android/issues?q=is%3Aissue+is%3Aclosed), to see if your issue is either already being addressed, or has been solved by someone else.
+
+If not, please feel free to fill in the following info so we can help faster!
 
 ### Step 1: Are you in the right place?
 

PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,5 @@
+Hey there! So you want to contribute to FirebaseUI? Before you file this pull request, follow these steps:
+
+  * Have you read [the contribution guidelines](CONTRIBUTING.md)
+  * Has this been discussed in an issue? If so make sure to mention the issue number here.  If not, go file an issue about this to make sure this is a desirable change.
+  * Are you adding a feature? If so please co-ordinate with someone on [FirebaseUI-iOS](https://github.com/firebase/firebaseui-ios) to make sure that we can implement this on both platforms and maintain feature parity.

README.md

@@ -131,4 +131,4 @@ accept your pull requests.
 1. Ensure that your code adheres to the existing style of the library to which
    you are contributing.
 1. Ensure that your code has an appropriate set of unit tests which all pass.
-1. Submit a pull request and cc @puf or @mcdonamp
+1. Submit a pull request and cc @puf or @samtstern