Not all builders want to run all deps' tests
Not all builders want to run all deps' tests

For example, some organisations do not use, nor have the time to
maintain, some deps, like riak_ensemble. This change adds an argument
`TEST_IGNORE` that will skip the eunit test running for the deps
assigned to the variable.

Example::

    make test TEST_IGNORE="riak_ensemble yokozuna"

Will run eunit, but skip those directories. Compile will still run.

basho/riak