Update build.gradle (#101)

* Update build.gradle

Load Android Gradle Plugin conditionally and change 'compile' to 'implementation'

* Update build.gradle

revert changes `implementation` to `compile` due to breaking change.

Author: SaeedZhiany

android/build.gradle

@@ -3,13 +3,18 @@ def safeExtGet(prop, fallback) {
 }
 
 buildscript {
-    repositories {
-        google()
-        jcenter()
-    }
+    // The Android Gradle plugin is only required when opening the android folder stand-alone.
+    // This avoids unnecessary downloads and potential conflicts when the library is included as a
+    // module dependency in an application project.
+    if (project == rootProject) {
+        repositories {
+            google()
+            jcenter()
+        }
 
-    dependencies {
-        classpath("com.android.tools.build:gradle:3.4.1")
+        dependencies {
+            classpath("com.android.tools.build:gradle:3.5.1")
+        }
     }
 }