* Increase test coverage to 93% #549

* cover missing AllowanceCrowdsale branch

* improve Heritable coverage

* fix lint errors

* proper equal assert

* address review comments

* remove unneeded const definitions and imports

* use assertRevert

* reword scenario description

* Increase test coverage to 93% #549

* cover missing AllowanceCrowdsale branch

* improve Heritable coverage

* fix lint errors

* proper equal assert

* address review comments

* remove unneeded const definitions and imports

* use assertRevert

* reword scenario description

* move HIGH_GOAL constant to the scope where it's used

* remove const at top level

* address review comments