Added mixin support. Updated gitignore.

build.gradle

@@ -1,3 +1,14 @@
+buildscript {
+    repositories {
+        // These repositories are only for Gradle plugins, put any other repositories in the repository block further below
+        maven { url = 'https://repo.spongepowered.org/repository/maven-public/' }
+        mavenCentral()
+    }
+    dependencies {
+        classpath 'org.spongepowered:mixingradle:0.7-SNAPSHOT'
+    }
+}
+
 plugins {
     id 'eclipse'
     id 'idea'
@@ -5,6 +16,8 @@ plugins {
     id 'org.parchmentmc.librarian.forgegradle' version '1.+'
 }
 
+apply plugin: 'org.spongepowered.mixin'
+
 group = mod_group_id
 version = mod_version
 
@@ -58,6 +71,12 @@ minecraft {
     }
 }
 
+mixin {
+    add sourceSets.main, "${mod_id}.refmap.json"
+
+    config "${mod_id}.mixins.json"
+}
+
 sourceSets.main.resources {
     srcDir 'src/generated/resources'
 }
@@ -66,6 +85,7 @@ repositories {}
 
 dependencies {
     minecraft "net.minecraftforge:forge:${minecraft_version}-${forge_version}"
+    annotationProcessor 'org.spongepowered:mixin:0.8.5:processor'
 }
 
 tasks.named('processResources', ProcessResources).configure {