Fixed "All Selected" problem on non-multiselect with one option

There’s some situation when there are only one option and that displays
“All selected” which is only correct if the select tag is “multiple”.
In using this plugin for “single” dropdowns as well, there are
situations when there’s only one option and it shouldn’t show “All
selected”. This fixes that

dist/js/bootstrap-multiselect.js

@@ -197,7 +197,11 @@
                 if (options.length === 0) {
                     return this.nonSelectedText;
                 }
-                else if (this.allSelectedText && options.length == $('option', $(select)).length) {
+                else if (this.allSelectedText 
+                            && options.length === $('option', $(select)).length 
+                            && $('option', $(select)).length !== 1 
+                            && this.multiple) {
+
                     if (this.selectAllNumber) {
                         return this.allSelectedText + ' (' + options.length + ')';
                     }