Move unscented types to new src file
include(unscented.jl)
Move sigma functions over to unscentedtypes.jl Add outer constructor for filter
Add unscented Kalman filter equations
Get rid of an old comment
Add additional outer constructor for filters. Calculate new sigma points from a filter.
Make it possible to access sigma points from a filter as well as recalculate them
Refactor the predict/update steps to make it possible to
predict repeatedly and then update.

Adds estimate method to calculate the estimated state associated with a set of sigma points
Add comment documentation for estimate methods
Export unscented types
Fix some variable name bugs
Add Van der Pol oscillator test
Remove some ambiguities reported by Lint.jl
Change some naming ambiguities
Fix typo that came out of rebase
Fix sigmas to play well with new return type of chol
Add UnscentedState as a subtype of AbstractState

Goal is to get the UnscentedKalmanFilters to look like
BasicKalmanFilters
Convert all of the AdditiveUnscentedKalmanFilter methods to use
the new UnscentedState

Includes a method for creating an UnscentedState from a State
Make Sigmas a more general typealias
Add folder for ukf tests