Fix issue #392 not changed value mask

[JosielFaleiros]

This pull request is to fix the problem found in the issue #392 , where the value do not get masked when the same value is pasted twice, but it should apply the mask in that case.

This code is working on a local build, and within a project where I am using this lib.

Improvement suggestions are welcome. :)

[probil]

@JosielFaleiros
Can you add tests as well please?

[JosielFaleiros]

Hi @probil

I would like to, but I am little busy these days, this will take some time, so any help from other devs for this are welcome too.

Thanks for the project!

[JosielFaleiros]

Hi @probil

I've added a test to verify the case explained, that will be fixed by this PR.
I hope you find it valid now.

[probil]

Hey @JosielFaleiros
I've check your PR and it works well for your case but doesn't work for another case.
It's impossible to remove placeholder symbol from the input.

1. Let's say I have mask ##:##
2. I have entered 1111, value became 11:11
3. I pressed backspace 2 times, value became 11:
4. I pressed backspace one more time but value is still 11:, expected result is 11
   So it stuck

I'm going to add this test to unit tests and will try to find a solution that handles both cases

[probil]

#415