add suggestionWrapper template

allows to supply a different suggestion wrapper template to allow finer control of the dropdown suggestions.

This is useful to display suggestions that need to appear disabled and should not be selectable or participate in the auto-complete.

Example of the "suggestionWrapper" template to change suggestion wrapper class to "tt-suggestion-disabled" if the suggestion data contains some flag:

    <div class="tt-suggestion{{#some_conditional_property}}-disabled{{/some_conditional_property}}"></div>

and the css for for "tt-suggestion-disabled":

    .tt-suggestion-disabled {
      padding: 8px 20px;
      font-size: 18px;
      line-height: 24px;
    }

    .tt-suggestion-disabled, .tt-suggestion-disabled.tt-cursor {
      color: #D1D0CE;
      cursor: pointer;
    }

    .tt-suggestion-disabled p {
      margin: 0;
    }