Don't allow creating OP with implicit Unchecked.defaultOf<_> initial value.
A -like operator for creating OPs.
Merge branch 'master' of bitbucket.org:blacktaxi/observable-property
Use the  operator to create OPs.
Fixed current value tracking.
Don't allow creation of OPs from Observables with implicit Unchecked.defaultOf<_> initial value.
Use  in tests.
Merge branch 'master' of github.com:blacktaxi/observable-property

Conflicts:
	src/ObservableProperty/ObservableProperty.fs