* Fixed a SplitPayment test

* Deleted unnecessary function.

* Improved PostDeliveryCrowdsale tests.

* Improved RefundableCrowdsale tests.

* Improved MintedCrowdsale tests.

* Improved IncreasingPriceCrowdsale tests.

* Fixed a CappedCrowdsale test.

* Improved TimedCrowdsale tests.

* Improved descriptions of added tests.