Add Racket 6.0.1 to .travis.yml
Use git to get latest install-racket.sh
Fix scribble conversion to work a little.
Merge pull request #41 from samth/master

Fix scribble conversion to work a little.
Delete debug printf from commit 2e7c6a3
More updates to xexprs->scribble-pres

- The markdown parser generates xexprs that always have attributes,
  including () for no attributes.

- Tables don't necessarily have a tbody

- Images are now in a div with caption.

- Plain code blocks are always `(pre () (code () ___))`.

This is still not 100% correct:

- See commented-out unit test for table -> tabular.

- Footnotes not yet handled.
Correctly expand tabs.

Want to commit a fix -- although I plan to remove tab-expansion
completely in the next commit.
Don't expand tabs in pre elements.

On reflection I think the correct thing to do is leave them as-is.

If someone wants to filter them, that's properly a job for something
like Pygments post-processing.

Plus you probably don't want to filter them. Consider the example of a
code block containing a makefile, where tabs are significant (IIUC).
Someone should be able to copy and paste that example.
Use `(list* x . more)` and `(,x . ,more)` match patterns.

Rather than `(list x more ...)` and `(,x ,more ...)`.

Former are faster, at least for big N.
Fix #42.

$fence-line-close needs a `try` so that it doesn't consume backticks
when the parse doesn't succeed.
Bump to v0.16