Remove bin/crystal usage for init tool specs

[bew]

It feels ugly to pass stderr all over the place, but hey.. it works!

I think that the routines getting the correct fields from the given args being in the class is not correct, we should probably build a intermediate object (kind of factory which takes arguments and 'parse' them) that will create & return the InitProject object then execute it or sth like that.. Absolutely not sure about this..

Maybe we should just merge this to remove bin/crystal direct usage, and make another PR to refactor the init tool? (I think I would prefer that)

WDYT?

[asterite]

To avoid passing stderr everywhere, make Init a class, store it in an instance variable, and change class methods to instance methods.

[bew]

@asterite the specs fails weirdly because there are early exits in the init tool, so when the spec check a specific error, it exits after printing a little msg on stderr. (no idea how I got the specs to pass once on my computer...)

I'm going in another way, using exceptions instead of STDERR.puts msg; exit 1, it should be better!

[RX14]

circleci seems to be flakey downloading things from homebrew, i've had to restart a number of builds.

[asterite]

I don't think we need two exception types here. Even just using plain Exception might be good, but just Error would be fine.

[bew]

@asterite I kept Error exception class only, should be GTG I think!