DeFiMath v2.0.0 released - API rename and finance primitives

Breaking change. All public functions have been renamed to drop the get prefix — for example, getCallPrice is now callOptionPrice. Update call sites when upgrading.

New math primitives:

• expm1 and log1p

New finance functions:

• compoundInterest
• presentValue
• logReturn
• continuousToDiscrete
• discreteToContinuous

Follow-up (v2.0.1): timeToExpirySec renamed to timeToExp.

Both compoundInterest and presentValue saw immediate gas optimizations after their first implementation.