Added Barrier option pricing code

Merton, Reiner, Rubinstein as described in Option Pricing Formulas,
 Haug.
Merge pull request #21 from og3b/master

Added Barrier option pricing code
Move test market data builders to trait
Remove old module from maker
Pivot Reports

Enough of a pivot reporting framework to run position and mtm
reports on a set of trades.

Unfortunately mixed in with this commit are some other changes
related to position calcs - namely
- Creation of a HedgingInstrument trait that has a volume
- Replaced SwapHedgeInfo and FuturesHedgeInfo with plain HedgeInfo
- To avoid confusion with FuturesMarket, the terms 'riskMarket' and
  'riskPeriod' are used in hedging (and position reporting).
Add pivot module to sbt
Add samples for each instrument