Allow ui-negative-number in ui-percentage-mask

[Konageski]

In percentage mask, analise the tag ui-negative-number e correct value
and mask

[coveralls]

Coverage decreased (-0.9%) to 96.388% when pulling 1aea674 on Konageski:master into 2ea6056 on assisrafael:master.

[coveralls]

Coverage decreased (-0.7%) to 96.571% when pulling 790f8a4 on Konageski:master into 2ea6056 on assisrafael:master.

[assisrafael]

I'm not sure about this change.
Can you implement a test case that shows the behavior you need?

[Konageski]

Today is not possible to use negative number in percentage-mask field.
This change able to use ui-negative-number in ui-percentage-mask field.
I use this change in my system.

<input type="text" name="negativePercentage" ng-model="obj.negativePercentage" class="form-control" ui-percentage-mask="2" **ui-negative-number** required>

[guylhermetabosa]

This definitely should be available in this lib. Thanks @Konageski.

[assisrafael]

Replaced by #300