Merge pull request #276 from casper-network/version-bump-2.5.7

Update build.gradle

Author: meywood

build.gradle

@@ -14,7 +14,7 @@ apply plugin: 'java'
 
 group = 'network.casper'
 // Version number update for release
-version='2.5.6'
+version='2.5.7'
 sourceCompatibility = 1.8
 targetCompatibility = 1.8