Ignore whitespace when adding and validating tags.

This commit addresses several bugs related to whitespace:

* You can no longer add a tags which consist entirely of whitespace
* You can no longer workaround the `minChars` validation by adding whitespace

Code changes are pretty minimal. Tests included for both these cases. Lemme
know if you have any questions.
Fixed typo: `trimInput` not `timmedInput`.
Merge pull request #27 from scholastica/disallow_whitespace_tags

Ignore whitespace when adding and validating tags