Added FsRx wrappers

The commented out functions depend on the .net 4.5 framework
pulled from upstream
Finished merge
Merge branch 'adding-fsrx' of https://github.com/cloudRoutine/FSharp.Reactive into merge
Continuous integration prep

* Elevate 'Reactive' to the namespace and restore use of 'Observable' as the module name
* Fix tests
* Fix build script