feat(tooltip): Prevent close tooltip with 'esc' key

[RDD2017]

Motivation

Tooltip must be shown if <input> tag isn't valid, but if user press 'ESC' key it closes tooltip and reset validation.

This PR introduce new option 'tooltip-enable-esc'.

If user set 'tooltip-enable-esc' as false, tooltip will not closed.

By default 'tooltip-enable-esc' is true.

How to use

        <input type="text"
               ng-model="amount"
               numbers-only
               tooltip-enable-esc="false"
               uib-tooltip="Amount field must be number"
               tooltip-enable="error"
               tooltip-is-open="error"
               tooltip-trigger="'none'"
               tooltip-placement="bottom" />