Bring theme up-to-spec and update screenshot

[jaminthorns]

Here are the changes:

• ANSI colors are brought up-to-spec. They were previously all incorrect when loaded into iTerm. I think this was mainly due to the colorspace not being included in the exported colors. The default colorspace for non-specified colors in iTerm might have changed since this theme was first developed (since it hasn't been updated in a while). It's now set explicitly to sRGB for each color (the default when exporting color presets).
• Foreground, background, and selection colors are brought up-to-spec. Also, the selection text color is set to AnsiBrightWhite. My reasoning for this is that the selection color is brighter than the background color, therefore the selection text color should be brighter than the foreground color for proper contrast.
• Links color is set to Cyan as per the spec.
• Cursor color is set to Foreground, and cursor text color is set to Background, meaning that the cursor and the text under it is inverted from the foreground/background colors.
• Badge color is set to Comment with 75% opacity.
• Cursor guide color is set to Comment with 25% opacity.

[jaminthorns]

@zenorocha Any chance we could get this merged?