Firebase emulator testing (#9)

- Firebase emulator added
 - Update to Espresso tests
 - Updated gradle dependencies for espresso
 - Updated config.yml
 - Updated android gradle version

app/src/debug/res/xml/network_security_config.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<network-security-config>
+    <domain-config cleartextTrafficPermitted="true">
+        <domain>10.0.2.2</domain>
+    </domain-config>
+</network-security-config>