Begin development of version 3.2.0

Change-Id: I040c43ccd37c33ba1844f6b93e292b0ed7010fe5

Author: samtstern

constants.gradle

@@ -1,7 +1,7 @@
 project.ext {
     submodules = ['database', 'auth', 'storage', 'firestore', 'common']
     group = 'com.firebaseui'
-    version = '3.1.3-SNAPSHOT'
+    version = '3.2.0-SNAPSHOT'
     pomdesc = 'Firebase UI Android'
 
     compileSdk = 27