Merge pull request #237 from caarlos0/master

Added GWT Project related paths to a new GWT.gitignore file.

GWT.gitignore

+*.class
+
+# Package Files #
+*.jar
+*.war
+
+# gwt caches and compiled units #
+war/gwt_bree/
+gwt-unitCache/
+
+# boilerplate generated classes #
+.apt_generated/
+
+# more caches and things from deploy #
+war/WEB-INF/deploy/
+war/WEB-INF/classes/
+