Allow string input for Kss::Parser

Allowing string input (with `Kss::Parser.new(string)`) allows dynamic use cases in live web applications

Example:

```ruby
buttons =<<-'EOS'
  /*
  Your standard form button.

  :hover    - Highlights when hovering.
  :disabled - Dims the button when disabled.

  Styleguide 1.1
  */
  button {
    padding: 5px 15px;
    line-height: normal;
    font-family: "Helvetica Neue", Helvetica;
    font-size: 12px;
    font-weight: bold;
    color: #666;
    text-shadow: 0 1px rgba(255, 255, 255, 0.9);
    border-radius: 3px;
    border: 1px solid #ddd;
    border-bottom-color: #bbb;
    background: #f5f5f5;
    filter: progid:DXImageTransform.Microsoft.gradient(GradientType=0, startColorstr='$start', endColorstr='$end');
    background: -webkit-gradient(linear, left top, left bottom, from(#f5f5f5), to(#e5e5e5));
    background: -moz-linear-gradient(top, #f5f5f5, #e5e5e5);
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.15);
    cursor: pointer;
  }
  button:disabled {
    opacity: 0.5;
  }
EOS
@styleguide = Kss::Parser.new(buttons)
```

We can then imagine a web app for prototyping designs or html components that would provide live kss documentation & demo rendering without relying on static files.
Fix javascript infinite loop in kss.js
Add string use case in the example app
Add string use case in the README.md
Document the CommentParser#parse_blocks method
Merge branch 'allow-string-input' of git://github.com/goodtouch/kss into goodtouch-allow-string-input
Merge pull request #1 from neonelectro/goodtouch-allow-string-input

kneath/kss PR 47: Allow string input for Kss::Parser