Merge remote-tracking branch 'pr/84'
add a demo for elixir
Add Racket lexer, and switch *.rkt to it from Scheme.

- .rkt, .rktd, .rktl files
- Accept   \u03BB lambda character
- Long list of keywords and very long list of builtins
- Numeric constants like -inf.0, +inf.0, -min.0, +max.0 and friends
- Add test (and adjust Scheme test)
- Add to visual/samples
racket: add detection for '#lang racket'
racket: fix indentation #cosmetic
Merge branch 'racket'
update the php builtins via `rake builtins:php`
racket: add lower-confidence guessing for #lang
racket: use a real λ, and include [:alnum:] in `id`

[:alnum:] will capture any unicode character designated as alphanumeric,
in particular greek and cryllic characters.
Updates to Racket lexer:

- Actually the \u03BB lambda char does work fine inside %w() with the
  others.
- Since Racket allows identifiers to consist of nearly anything,
  instead of describing what they are, describe what they are _not_.
- Handle quasiquote as well as quote.
Merge pull request #87 from greghendershott/racket-lexer-ids

Updates to Racket lexer
v0.3.9
add the license to the gem source
add a link to the wiki instructions to the README
add `license` to the gemspec
add a lexer for R (r-project.org)
Omit whitespaces when lexing Elixir's keywords.

This commit fixes #89.
v0.3.10
Merge remote-tracking branch 'pr/90'
add the :inline_theme option to Formatters::HTML

Given a CSSTheme, this will inline the styles from the theme into the
<span> tags, allowing the content to be included in contexts where
stylesheets aren't appropriate, like emails.