TestMathlib.sol: Test collateral for a long position and price equal to priceFloor.
TestMathlib.sol: Test collateral for a long position and price equal to priceFloor.

Verify in testCalculateNeededCollateral that needed collateral for a long position
and price equal to priceFloor is 0.

Issue: #27

MarketProject/MarketProtocol,MarketProject/MarketProtocol