Fix bug with invalid characters in parse_number and add the proper test.

I notice that when you try to parse a number like this '1-*304-8879463', it returns '-*304-8879463' (without removing the non-numeric characters), even further, when you try to parse a number with special characters and things that shouldn't be there, it was keeping them, so I made the following changes:

1-Add clear in the input number in parse_number before start procesing it.
2-Make more tests to parse_number, checking the case when the number contains invalid characters.