Support for Hangfire 1.0

There were some breaking changes in Hangfire 1.0, and this PR contains fixes for these changes:

* Hangfire.SimpleInjector targets .NET Framework 4.5 now.
* `Hangfire.Core` dependency updated to version `1.0.1`.
* Namespaces changed to `Hangfire.*` (lowercased `f` letter).

I've also changed the version of `Hangfire.SimpleInjector` to `1.2`, but I can't push it to NuGet, since I'm not an owner of the package.