Support for applying completion item background with textmate color schemes

[PranavPurwar]

You can now apply the completion item background when using TextMateColorScheme by modifying the textmate theme.

Example

{
  "name": "darcula",
  "settings": [
    {
      "settings": {
        "completionWindowBackground": "#1F1A1B",
        "completionWindowBackgroundCurrent": "#1F1A1B"
      }
    }
  ]
}

[Rosemoe]

Thanks for your contributions