Fix/2173 only accept int numeric answers

[leandroradusky]

Close #2173.

In Elixir,

iex(2)> Integer.parse("22.1")
{22, ".1"}
iex(3)> Float.parse("22.1")  
{22.1, ""}

Then, the methods is_numeric_permissive & is_numeric were accepting float values and passed them through.

While before it was continuing with the survey, now:

Note: is easy to round the integer part and get it: I moved forward accepting integers strictly, and returning false otherwise (and not the number rounded to an integer).

Note 2: this was happening only in SMS mode (it couldn't happen in phone channels ─an error is thrown upon responses containing # or *─, neither in the mobile web mode, where ─at least in the simulator─ the validation is performed well.

[ysbaddaden]

Well found! Could you add tests in test/ask/runtime/flow_test.exs? There are a number of examples under describe "numeric steps", but having a few tests around floats would help.