Unable to delete characters from Spinner's input field (Firefox only)

[khrise]

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Plunkr Case (Bug Reports)
No plunkr provided, as the issue can be reproduced on the demo page.

Current behavior
In Firefox, when a value has been entered into a spinner's input, it can't be deleted again. In fact, all keys get captured, it is not even possible to hit F12 and open the developer tools without clicking somewhere outside the input field.

Expected behavior

• Only relevant keys's events get stopped from propagation
• Characters can be deleted via backspace and delete button
• Right and left arrow keys can be used to navigate the cursor in the input field

Minimal reproduction of the problem with instructions
Using Firefox, go to the demo page, enter a value into one of the spinners and try to delete any of the characters from the input or navigate with the left/right arrows.

What is the motivation / use case for changing the behavior?

Please tell us about your environment:
Windows 7 Professional, Firefox 45.7.0

• Angular version: 2.0.X

• PrimeNG version: ^2.0.0-rc.2

• Browser: Firefox 45.7.0

• Language: [all | TypeScript X.X | ES6/7 | ES5]

• Node (for AoT issues): node --version =