Added helper module for 'Octopus Tools' (Octopus Deploy)

Example usage:

```
/// Creates a release from the latest pushed nuget package and deploys to test environment.
Target "OctoReleaseAndDeploy" (fun _ ->

    let release = { releaseOptions with Project = "My Web Service" }
    let deploy  = { deployOptions with DeployTo = "Test Environment" }

    Octo (fun octoParams -> 
        { octoParams with
                     ToolPath = "./packages/octopustools";
                     Server = { Server = "http://octopus.com/api"; ApiKey = "YOUR-BUILD-SERVER-API-KEY-HERE" };
                     Command = CreateRelease (release, Some deploy); }
    )     
)
```