[WIP] Get concrete working with latest  relx

* Added dialyzer.mitigate to get prevent eunit dialyzer warning from breaking build (Warnings as errors)
* Bump to use version 1.0 of relx, which (will) contains a fix that was breaking builds produced by concrete

***NOTE***: This will NOT work until relx 1.0 is released, which is expected this weekend, hopefully today.