Temporarily add exoplayer repo accidentally deleted from jcenter (#977)

diff --git a/packages/camera/example/android/build.gradle b/packages/camera/example/android/build.gradle
index bb8a303..db72880 100644
--- a/packages/camera/example/android/build.gradle
+++ b/packages/camera/example/android/build.gradle
@@ -13,6 +13,9 @@
     repositories {
         google()
         jcenter()
+        maven {
+            url 'https://google.bintray.com/exoplayer/'
+        }
     }
 }
 
diff --git a/packages/image_picker/android/build.gradle b/packages/image_picker/android/build.gradle
index 70ee798..b6ac95b 100755
--- a/packages/image_picker/android/build.gradle
+++ b/packages/image_picker/android/build.gradle
@@ -16,6 +16,9 @@
     repositories {
         google()
         jcenter()
+        maven {
+            url 'https://google.bintray.com/exoplayer/'
+        }
     }
 }
 
@@ -23,7 +26,7 @@
 
 android {
     compileSdkVersion 27
-    
+
     defaultConfig {
         minSdkVersion 16
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
diff --git a/packages/video_player/example/android/build.gradle b/packages/video_player/example/android/build.gradle
index bb8a303..db72880 100644
--- a/packages/video_player/example/android/build.gradle
+++ b/packages/video_player/example/android/build.gradle
@@ -13,6 +13,9 @@
     repositories {
         google()
         jcenter()
+        maven {
+            url 'https://google.bintray.com/exoplayer/'
+        }
     }
 }