Removed empty term validation.

Why are you validating that term is filled? If I want to suggest values immediately after opening select2 input, I specify select2_options {"minimumResultsForSearch": 0, "minimumInputLength": 0,}.

Why isn't this valid case? Maybe I'm missing something, but see it very useful to suggest, for example, last used values immediately after opening select2 field.

Thanks!
Merge pull request #52 from Ameriks/master

Removed empty term validation.