Indentation with match_clause=4
Tentative fix for #17

Probably wrong as untested. Still pushing to review.
Add PreCode, Verbatim and Block nodes

Related to #18 (and others?)
Parse the Code, PreCode and Verbatim blocks in cmi/cmtis
Store title's label and level in attributes
Fix indentation
Fix handling of external targets

Fix #10
Add support for link targets in doc comments

Fix #11
Workaround a bug in the ocamldoc parser

Related to #14
Display unimplemented text nodes

It's easier to debug
Display all the non-implemented nodes

No more Not_implemented exceptions, now all the unimplemented bits appears in the generated document.
Add support for exceptions

Fix #21
Support tags

Fix #22
Call some magic runes before invoquing read_extension_constructor
Give a proper abstract type to exception names
Remove the `Block` node
Better encoding of tags

It's maybe better to put some information in the attributes instead, but well...
Fix handling of optional labels

Fix #28
Merge pull request #24 from samoht/master

Start fixing some of the issues