switch to anatawa12 fork of forgegradle 2.3

Fix failing asset task due to switch to https

build.gradle

@@ -7,9 +7,10 @@ buildscript {
         maven { 
             url = 'https://repo.spongepowered.org/maven' 
         }
+	mavenCentral()
     }
     dependencies {
-        classpath 'net.minecraftforge.gradle:ForgeGradle:2.3.4'
+	classpath 'com.anatawa12.forge:ForgeGradle:2.3-1.0.7'
         if (project.use_mixins.toBoolean()) {
             classpath 'org.spongepowered:mixingradle:0.6-SNAPSHOT'
         }