r date examples, asset swap, inst changes, docs (goldmansachs#154)

regen instrument targets, new date func (goldmansachs#153)

doc updates, new timeseries measure, backtesting func (goldmansachs#152)

Update utils.py (goldmansachs#151)

new instruments, notebooks (goldmansachs#150)

Update instrument.py (goldmansachs#148)

new instruments, event notebooks (goldmansachs#147)

doc update, carry changes (goldmansachs#146)

new and updated class definitions (goldmansachs#145)

updated examples and mkt data fix (goldmansachs#144)