QuickCheck models for aeternity/epoch

Suggested workflow

• Check out this repo into e.g. epoch/eqc
• Start a shell using rebar3 (from epoch/): ./rebar3 as test shell --apps=""
• Move into the directory containing the models you would like to run, e.g.: 1> cd("eqc/aeutils_eqc").
• Compile the model, e.g.: 2> c(aeu_mp_trees_eqc).
• Run the tests, e.g.: 3> eqc:quickcheck(aeu_mp_trees_eqc:prop_insert_delete()).