Support for .sublime-color-scheme file format

[simov]

Here is how I (dirty) fixed Rainbolth to work with the new .sublime-color-scheme file format.

1. Clone this repo in your ~/.config/sublime-text-3/Packages
2. Open rainbowth.py and add the following line inside the update_color_scheme method:

     print("Rainbowth: color scheme needs updating")
+    return colors

3. Add the palette colors to your .sublime-color-scheme file:

{
  "name": "rainbowth0",
  "scope": "rainbowth0",
  "foreground": "Red",
  "background": "#000001"
},
{
  "name": "rainbowth1",
  "scope": "rainbowth1",
  "foreground": "Chartreuse",
  "background": "#000001"
},
{
  "name": "rainbowth0",
  "scope": "rainbowth0-lineHighlight",
  "foreground": "Red",
  "background": "#000001"
},
{
  "name": "rainbowth1",
  "scope": "rainbowth1-lineHighlight",
  "foreground": "Chartreuse",
  "background": "#000001"
},

The above configuration have only 2 colors, but you can add more - rainbowth2, rainbowth3 and so on:

The above #000001 background color is for dark color schemes. It's important to use this color instead of plain black #000000 because otherwise Sublime inverts the values. If you use lighter color scheme choose another background color.

[five-vee]

With monokai, this worked for me. It's got 5 alternating (from hot to cold colors)

        {
          "name": "rainbowth0",
          "scope": "rainbowth0",
          "foreground": "Red",
          "background": "#272822"
        },
        {
          "name": "rainbowth1",
          "scope": "rainbowth1",
          "foreground": "Chartreuse",
          "background": "#272822"
        },
        {
          "name": "rainbowth2",
          "scope": "rainbowth2",
          "foreground": "Orange",
          "background": "#272822"
        },
        {
          "name": "rainbowth3",
          "scope": "rainbowth3",
          "foreground": "Cyan",
          "background": "#272822"
        },
        {
          "name": "rainbowth4",
          "scope": "rainbowth4",
          "foreground": "Yellow",
          "background": "#272822"
        },
        {
          "name": "rainbowth0",
          "scope": "rainbowth0-lineHighlight",
          "foreground": "Red",
          "background": "#272822"
        },
        {
          "name": "rainbowth1",
          "scope": "rainbowth1-lineHighlight",
          "foreground": "Chartreuse",
          "background": "#272822"
        },
        {
          "name": "rainbowth2",
          "scope": "rainbowth2-lineHighlight",
          "foreground": "Orange",
          "background": "#272822"
        },
        {
          "name": "rainbowth3",
          "scope": "rainbowth3-lineHighlight",
          "foreground": "Cyan",
          "background": "#272822"
        },
        {
          "name": "rainbowth4",
          "scope": "rainbowth4-lineHighlight",
          "foreground": "Yellow",
          "background": "#272822"
        },