Update dotnet cli in Mac OSX

The version 1.0.0-preview2-003121 of the .Net CLI is currently the latest released version. So there is no newer released version to upgrade to.

You could upgrade to the latest build from the dotnet/cli repo, but you probably shouldn't, since that's not a released version.

To update from 2.0.3 to 2.1.4 I simply downloaded the installer from Microsoft's website and then ran the installer.

`https://download.microsoft.com/download/1/1/5/115B762D-2B41-4AF3-9A63-92D9680B9409/dotnet-sdk-2.1.4-osx-gs-x64.pkg

I had a Terminal window open, and when I did a dotnet --version before and after running the installer, the correct version was output to the console. I did not have to restart my terminal window even.