fix(datepicker): change trigger event for NgbInputDatepicker

[PerfectPixel]

Changes the trigger event in NgbInputDatepicker for manual date change from change to inputas discussed in #1225.

[pkozlowski-opensource]

@PerfectPixel thnx for the PR, it looks good. One question though - did you test it on IE10/11 and / or Edge? I recall that there are some issues with how the input event is handled in those browsers and I would like to verify that we are not breaking code on those browsers (existing unit tests won't catch those issues, unfortunately...)

[PerfectPixel]

@pkozlowski-opensource ok there is a rub. This line causes the following behaviour:

1. User types "2017"
2. "2" is not a valid NgbDate -> this._model = null, therefore, _onChange = '2' and the input is overwritten with null by _writeModelValue(null)
3. "0" becomes the first number again as the input was reset with null.
4. and so on...

Here is a gif where I am typing numbers randomly.

The easiest solution is to uncomment this line. However, there are a few changes in behaviour:

1. Typing a year + month and press enter no longer autocompletes the input to year + month + 1st of month (although the model stays the same).
2. Lets you input letters.
3. If you have a valid date like 2017-06-05 and delete the 05, you'll end up with 2017-06- as the model. If you delete the last dash, you get a valid NgbDate again.

Edit: The input event itself works fine using IE 11 and Edge

[PerfectPixel]

@pkozlowski-opensource have a look at my last commit. This fixes the input. Also, it mitigates the first issue as I introduced a change event that updates the view with the model enabling autocomplete of the day once again. The 2nd and 3rd issues are also happening in the original version just on a different event.

[pkozlowski-opensource]

@PerfectPixel it all looks good to me! We've got a big PR for date picker in-flight (keyboard navigation) so I'm going to wait with merging till the end of the week (so other PR can land first).

Thnx!

[pkozlowski-opensource]

@PerfectPixel the other PR I've mentioned just landed so we can get in this one. Would you mind rebasing so we can land your PR?

[PerfectPixel]

Not at all, I'll have a look at it tonight

[PerfectPixel]

@pkozlowski-opensource all done :-)