vsce show on powershell/cmd prints unknown characters

**Repo steps**
1. In windows powershell or cmd
2. Run `vsce show eamodio.gitlens`

**bug**
The stars and download symbol are printed as unknown characters

![capture](https://user-images.githubusercontent.com/12821956/33625634-06eeea46-d9ad-11e7-850e-d4bcd3337784.PNG)
