Adding the version number of the Java Dependency. (#497)

closes #380

Author: nicolasgarnier

README.md

@@ -1019,7 +1019,7 @@ To set up a development environment to build FirebaseUI from source, you must
 have the following installed:
 - Node.js (>= 6.0.0)
 - npm (should be included with Node.js)
-- Java Runtime Environment
+- Java SE Runtime Environment 8
 
 In order to run the demo and tests, you must also have:
 - Python (2.7)