Incorrect splitting when body contains delimiter

[rubenv]

When the body of a file contains a delimiter, incorrect parsing occurs.

I haven't yet found a good way to fix this (the use of SplitFunc makes it a bit difficult to reconstruct the original text and I have yet to figure out the best way to simply make it stop splitting), but for now here's a unit test to illustrate things.

[rubenv]

Am thinking we'll need to change *Matter.split(), so that it only splits twice (once before front matter, once after). But to do that we'll need to keep track of the number of splits that have happened.

Sadly I see no way to do so without putting state into *Matter, which would break thread-safety.

[snipem]

I found this to be a problem with an asciidoc file with a ditaa diagram containing --- lines.