Add Gradle build script

build.gradle

@@ -0,0 +1,31 @@
+buildscript {
+    repositories {
+        maven { url 'http://dl.bintray.com/jetbrains/intellij-plugin-service' }
+    }
+}
+
+plugins {
+    id "org.jetbrains.intellij" version "0.2.5"
+}
+
+dependencies {
+    compile files('lib/antlr4-runtime-4.6.jar')
+}
+
+apply plugin: 'idea'
+apply plugin: 'org.jetbrains.intellij'
+apply plugin: 'java'
+
+sourceSets {
+    main {
+        java {
+            srcDirs = ['src/main/java', 'adaptor/src', 'gen/']
+        }
+    }
+}
+
+intellij {
+    version 'IC-2016.3' //IntelliJ IDEA 2016.3 dependency; for a full list of IntelliJ IDEA releases please see https://www.jetbrains.com/intellij-repository/releases
+    plugins 'coverage' //Bundled plugin dependencies
+    pluginName 'Ballerina-IntelliJ-Plugin'
+}