Run dialyzer for extra_src_dirs

[Yozhig]

Usage:

1. Command rebar3 as test dialyzer adds modules from test directories for check due to the fact that rebar3 adds "test" to extra_src_dirs in test profile.

OR

2. Add directories you want to run dialyzer also on to extra_src_dirs in your rebar.config:

{profiles, [
    {dp, [{extra_src_dirs, ["tests"]}]}
]}.

and run rebar3 as dp dialyzer

[ferd]

Sounds like it should work fine. I'm going to live it open for a while and go try it and see what happens. Otherwise I know other folks had used Dialyzer on tests a whole lot, maybe @elbrujohalcon ? Might be nice to have him give it a spin.

[elbrujohalcon]

I do generally run dialyzer on tests, that's right. But I generally don't do it with rebar3. I use katana-test.