New: update gitignore file

.gitignore

@@ -0,0 +1,36 @@
+#built application files
+*.apk
+*.ap_
+
+# files for the dex VM
+*.dex
+
+# Java class files
+*.class
+
+# generated files
+bin/
+gen/
+
+# Local configuration file (sdk path, etc)
+local.properties
+
+# Windows thumbnail db
+Thumbs.db
+
+# OSX files
+.DS_Store
+
+# Eclipse project files
+.classpath
+.project
+
+# Android Studio
+*.iml
+.idea
+.gradle
+build/
+keystore.properties
+*.patch
+*.keystore
+gradle/wrapper/gradle-wrapper.properties