start updating for new set of upstream packages

[alecloudenback]

Migration Guide:

The shape and API of the package is mostly unchanged. The changes that have made fall into a few categores:

• Accommodating FinanceModels.jl, the next-generation version of Yields.jl. Release notes here
• Simplifying the API, generally making function calls require more specific arguments to avoid ambiguity
• Accommodating the new Cashflow type which makes modeling heterogeneous assets and liabilities simpler.

API Changes

• Breaking: The functions europut and eurocall have been moved to FinanceModels
• Breaking: Previously, the first argument to present_value or present_values would be interpreted as a set of Periodic(1) one-period forward rates if a vector of real values was passed. Users should explicitly create the yield model first, instead of relying on the implicit conversion:

# old 
pv([0.05,0.1], cfs)  

# new
using FinanceModels
y = fit(Spline.Linear(),ForwardYields([0.05,0.1]),Bootstrap())
pv(y,cfs)

• integrate Cashflow
• remove generator-accomodating functions if create ambiguous methods
• determine if breaking changes
• pv has been moved to FinanceCore