Merge pull request #5 from panesofglass/v2

Update to Rx 2.0
Merge pull request #6 from panesofglass/master

Fix a bad merge collision in the build script.
Fix the Observable.Create

http://stackoverflow.com/questions/13691710/augmenting-observable-create-for-f
Thanks, David Terk.
Using the latest FAKE version
Using the latest FAKE version
Using the latest nuget version
Using the latest FSharp version
Removing NaturalSpec
Using the latest FSharp version
Using the latest nuget version
Using the latest nuget version
Package restore fixed
Fix reference to NuGet.exe.
Merge branch 'master' into style

Conflicts:
	src/Observable.fs
Update the build script.