Add com.github.vlsi.checksum-dependency plugin to verify plugin and dependency artifacts

.travis.yml

@@ -7,6 +7,8 @@ env:
   global:
     - ANDROID_TARGET=android-15
     - ANDROID_ABI=armeabi-v7a
+    - ORG_GRADLE_PROJECT_checksumFailOn=build_finish
+    - ORG_GRADLE_PROJECT_checksumPrint=true
 
 android:
   components:

README.md

@@ -34,7 +34,7 @@ dependencies {
 
 You can see what to best use for ```<current_version>``` in the jitpack badge on the top.
 
-Please consider using [gradle witness](https://github.com/WhisperSystems/gradle-witness) to improve security.
+Please consider using [checksum-dependency-plugin](https://github.com/vlsi/vlsi-release-plugins#checksum-dependency-plugin) to improve security.
 
 ## Requirements