Added assertions to leaf initializers of (some) pseudo-abstract contr…

[nventuro]

Fixes #22 (partially)

MintedCrowdsale, FinalizableCrowdsale and PostDeliveryCrowdsale are also leaf contracts, but they have no initialize function: I opted for not adding an empty one with these checks to them, so coverage is not complete. The situation should be better than before this PR, though.

Test coverage will decrease until sc-forks/solidity-coverage#269 is fixed.

[coveralls]

Pull Request Test Coverage Report for Build 68

• 8 of 8 (100.0%) changed or added relevant lines in 7 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.7%) to 99.055%

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Totals
Change from base Build 63:	-0.7%
Covered Lines:	585
Relevant Lines:	585

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💛 - Coveralls

[spalladino]

I'm not sure I like coupling every derived contract to its parent's internal structure. How about adding an internal view _hasBeenInitialized() method to every crowdsale, and asserting that on the children?

[nventuro]

I was going to do that at first, but wanted to keep this as unobtrusive as possible. If you think that's a good idea though, I'll gladly implement it.

Any ideas on the ones without initialize functions?

[spalladino]

I think it'll be much more clear. As for the contracts without initialize functions, I'm fine with either skipping them, or adding a _hasBeenInitialized() { return true; } implementation.

[nventuro]

@spalladino can you take another look at this? Thanks!