Make it (sort of) work with react-marked

In order to wrap code blocks in Frame components we need the output of marked to be React components instead of a HTML string. marked relies on string concatenation internally, so I replaced it with react-marked which provides the expected functionality.

Obiously, the `createSections` function is broken by that.
Fix link
Bring back sections
Wrap code in iframes
Clean up
More robust styles for sidebar links

Prevent them from being easily overridden by a global `a` declaration.
Fix codeblock background helpers.
Tweak cg-Page children lists and paragraphs.
List styles
CoffeeScript optimization
Use custom Marked -> React transformation

react-marked had some problems with parsing and doesn't make much sense because marked should be used as a library, not be forked wholesale. Of course, this way we're very tightly bound to marked, but a more flexible (array-based instead of string-based) parser should be part of marked.
Add marked as dependency
Use react-frame-component module again
Require explicit package versions

The caret flag for semver covers a _very_ broad range of versions, which can lead to unexpected failures. We should specify exact versions or at least stick to the tilde flag to prevent this. We can do this because these are devDependencies only and thus don't break other packages.
Toggle iframe rendering of components
Merge branch 'iframe'
DIST 1.0.0-alpha-4