add TLA button example

.gitignore

 *.prob
 *.DS_Store
+*.aux
+*.fuzz
+*.log
+*_tla.txt

Button/TLA/button.json

+{
+  "svg": "../button.svg",
+  "items": [
+    {
+      "id": "button",
+      "attr": "fill",
+      "value": "IF button=TRUE THEN \"green\" ELSE \"red\" END"
+    },
+    {
+      "id": "button",
+      "attr": "stroke-width",
+      "value": "IF ENABLED(\"press_button\") THEN 6 ELSE 1 END",
+      "ignore": "is now used in hover below"
+    },
+    {
+      "id": "button_%0",
+      "attr": "visibility",
+      "value": "\"hidden\"",
+      "repeat": [ "TRUE", "FALSE" ]
+    }
+  ],
+  "events": [
+    {
+      "id": "button",
+      "event": "toggle_button",
+      "hovers": [{ "attr":"stroke-width", "enter":"6", "leave":"1"},
+                 { "attr":"opacity", "enter":"0.8", "leave":"1.0"}]
+    }
+  ]
+}

Button/TLA/button.tla

+------------------------------- MODULE button -------------------------------
+
+VARIABLES button
+
+Init == button = FALSE
+
+Press_Button == button' = TRUE
+ 
+toggle_button ==  button' = \lnot button
+
+Next == \/ Press_Button 
+	    \/ toggle_button
+
+Spec == Init /\ [][Next]_button
+
+=============================================================================
\ No newline at end of file