Added new option tabAutocomplete

[Artistan]

same update as #77 but without conflicts.
credit --> @Darnokk https://github.com/Darnokk

  - The default behaviour of the TAB-key is to select the top suggestion
  - We introduced a new option called 'tabAutocomplete' which is NOT mandatory and defaults to true.
  - If the option 'tabAutocomplete' is true, the TAB-key will select the top suggestion as usual
  - If the option 'tabAutocomplete' is NOT set, the TAB-key will select the top suggestion as usual
  - Only if you set the option 'tabAutocomplete' to false pressing the TAB key will change the focus on the html-element with the next tabindex.
  - Added option 'tabAutocomplete' to doc
  - Added two methods for tabAutocomplete = true resp. false to the unit-test typeahead_spec.js

[Artistan]

here is a bit of a work-around for anyone looking to allow for "not autocompleting".

https://codepen.io/Artistan/pen/LywrXj

[jcrben]

Seems cool, but why the changes to the minified files and the stuff like typeof exports === "object"?

Also, are you interested in becoming a maintainer? I no longer use this library.

[Darnokk]

I tested your dist/typeahead.bundle.js and saw no difference in the behaviour, when tabAutocomplete = true/false,
maybe there is a slightly mistake in there?

[Artistan]

no longer using... on to other things.