Fix disconnect method, update build.gradle, smaller fixes

Author: Louuke

.gitattributes

@@ -0,0 +1,6 @@
+#
+# https://help.github.com/articles/dealing-with-line-endings/
+#
+# These are explicitly windows files and should use crlf
+*.bat           text eol=crlf
+

.gitignore

@@ -0,0 +1,11 @@
+# Ignore Gradle project-specific cache directory
+.gradle
+
+# Ignore Gradle build output directory
+build
+
+# Ignore WhatsApp credential key storage
+credentials.json
+
+# Ignore WhatsJava fat jar
+/build/libs/WhatsJava-all.jar