Use golang to setUp & tearDown for tests

[gwennlbh]

Right now the makefile approach does not even work on MacOS, because it seems like trap '$(MAKE) mocks-teardown' EXIT is ignored and runs immediately (thus tearing down mocks before the tests run).

Also, for windows, it seems like a mess to support it, considering that it's not trivial on MacOS (which is also a *NIX)

Using golang for this:

• Makes the Makefile cleaner
• Improves the 'making tests run on all platforms' situation