fix backspace event for android

[d42f]

http://stackoverflow.com/questions/25043934/is-it-ok-to-ignore-keydown-events-with-keycode-229/25509350

Input has placeholder and mask +0 999 999 99 99. On android device (nexus 7 android 6) if press backspace then catch event with key code 229, not 8.

[lukepfeiffer10]

I'm hesitant to accept this change because a quick Google search on the key code 229 does not necessarily indicate a backspace key press. It actually seems to just represent the browser being told the input buffer is busy and not finished accepting input which is most likely the case on the android keyboard especially if it has autocomplete or word suggestion enabled.

[d42f]

@lukepfeiffer10 ok, I'll try to make demo tomorrow

[mrsnowin]

Just made the same changes to mask.js, and wanted to make pull request because my nexus 3 generate code 229 when backspace. But here it is :)

[ivanovevgeny]

I can confirm this PR solves the issue #123