Theme support and new terminal icon

I must mention I also included a custom builder for future reference. It currently doesn't work because atom is being silly and not recognizing string interpolation in class names. (Will raise this issue when I get back home tomorrow - if you want to report it yourself it'd be better)
``` css
.custom(@var) { .name-@{var} { color: red; } }
.custom(sample);
```
It should compile to:
``` css
.name-sample { color: red; }
```
But currently it's not working. Check it for yourself if you want by uncommenting last lines on colors.less. Finally, feel free to ignore my commit with the Custom builder on the Pull Request, since I only put it there to make it available when atom fixes that.

Also, I added theme support for all currently available themes for base16 scheme. Here is the source code I used to do it:
```ruby
#!/usr/bin/env ruby
require "yaml"

themes = Dir["*.yml"]

themes.each do |theme|
  less = []
  theme_name = File.basename theme, '.yml'

  yml = YAML.load_file(theme)
  yml.each do |key, value|
    next unless key.to_s.match(/(base0[89a-fA-F])$/)
    less << "@#{key}: ##{value};"
  end

  File.open("less/#{theme_name}.less", 'w+') do |file|
    file.write(less.join("\n"))
  end
end
```
Just put it into a folder with [base-16 builder ymls](https://github.com/chriskempson/base16-builder/tree/master/schemes) and it will output a .less file inside a /less folder (It only outputs base08~0F, so author, schemes, and other keys won't be present in the output.less). This way, if they release more themes you can quickly implement them here.