Add description of new option.accordion to README file

Author: mattez

readme.md

@@ -38,6 +38,14 @@ To activate tab collapse just include **bootstrap-tabcollapse.js** somewhere in
 
     $('#myTab').tabCollapse();
 
+By default tab collapse behave like accordion (always only active panel is visible / uncollapsed).
+If you want to use simple collapse (more panels can be visible/uncollapsed at the same time),
+set option "accordion" to "false":
+
+    $('#myTab').tabCollapse({
+        accordion: false
+    });
+
 If you want to specify the class that is given to accordion and tabs components you can do so by passing options to `tabCollapse`:
 
     $('#myTab').tabCollapse({