Update gradle to 4.2.1 version.

Signed-off-by: Yahor Berdnikau <egorr.berd@gmail.com>

dependencies.gradle

@@ -2,7 +2,7 @@ ext.versions = [
         minSdk               : 14,
         targetSdk            : 22,
         compileSdk           : 22,
-        gradle               : '4.1',
+        gradle               : '4.2.1',
 
         buildTools           : "25.0.3",
         androidTools         : "2.3.3",

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,5 @@
-#Mon Aug 21 21:36:22 CEST 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.2.1-all.zip