feat(deps): Add FirebaseUI

Change minSdkVersion back to 24
- Migrate to new Cloud Firestore

app/build.gradle

@@ -5,11 +5,12 @@ android {
     buildToolsVersion "26.0.2"
     defaultConfig {
         applicationId "com.edricchan.studybuddy"
-        minSdkVersion 21
+        minSdkVersion 24
         targetSdkVersion 26
         versionCode 6
         versionName "1.0.0-beta.920"
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        resConfigs "en"
     }
     buildTypes {
         release {
@@ -35,9 +36,12 @@ dependencies {
     testCompile 'junit:junit:4.12'
     // Firebase stuff
     compile 'com.google.firebase:firebase-storage:11.4.2'
-    compile 'com.google.firebase:firebase-database:11.4.2'
+    compile 'com.google.firebase:firebase-firestore:11.4.2'
     compile 'com.google.firebase:firebase-auth:11.4.2'
     compile 'com.google.android.gms:play-services-auth:11.4.2'
+    compile 'com.firebaseui:firebase-ui-auth:3.1.0'
+    compile 'com.firebaseui:firebase-ui-firestore:3.1.0'
+    compile 'com.firebaseui:firebase-ui-storage:3.1.0'
     // Provide a way to update the app
     compile 'com.github.javiersantos:AppUpdater:2.6.3'
     // Chrome Custom Tabs