Completing Paket conversion!

This completes the work started by @forki in #276. 

As discussed in the other thread, this does not change anything about how Deedle is consumed (we still publish a NuGet package, with the same things as before). 

However, this changes how we reference other packages. Rather than using NuGet directly, this uses it through Paket, but under the cover, it still gets the packages from NuGet. 

The nice things about Paket (and why I would like to use it for Deedle are):

 - Easier maintenance of `fsproj` files - when we update a reference, we just run `paket install` and that will update the `fsproj` files (so no more messing with `<HintPath>` elements by hand)
 - It handles versions in a simpler way, so the dependencies in `packages` do not contain version number in the folder name (this means we do not have to modify `*.fsx` files when we update a version of a referenced package).
 - The really nice thing is that we can also add dependencies on files from GitHub (see [docs](http://fsprojects.github.io/Paket/github-dependencies.html)). We could use that to get rid of the F# Data dependency (which causes various pains with versioning etc.) because we could reference CSV parser in this way.