Update docs: Modify compileSdkVersion, buildToolsVersion (#1056)

- compileSdkVersion 25
- buildToolsVersion "25.0.1"

docs/installation-android.md

 	
 2. Update project dependencies in `build.gradle` under `app` folder.
 	```groovy
+	android {
+	    compileSdkVersion 25
+	    buildToolsVersion "25.0.1"
+	    ...
+	}
+
 	dependencies {
 	    compile fileTree(dir: "libs", include: ["*.jar"])
 	    compile "com.android.support:appcompat-v7:23.0.1"
 	    }
 	}
 	```
-6. Run `react-native start`
+6. Run `react-native start`