Add 'displayKey' in the example in docs

[bitcity]

Just a minor change in docs :

I copied the bloodhound integration example and plugged in the engine described here but my search suggestions showed up as undefined (count was correct, but value was undefined). After tinkering with the examples, I found that displayKey : 'val' should have been specified in the typeahead initialization.

See this fiddle. The first box doesn't have displayKey set, hence suggestions are undefined. This is fixed in the second box by defining displayKey.

[jharding]

Thanks for bringing this to my attention.