Module Fails to Install

The following fails when using `0.13.3` of ScriptCs

`scriptcs -install -g ScriptCs.FSharp -Pre`

**Details**
`Installing packages...`
`ERROR: Package installation failed: Input string was not in a correct format..`

**My Setup**
`PS C:\code> svm list`
`scriptcs version manager - 0.3.8`
`The following scriptcs versions are installed:`
`*  0.13.3`
