Remove useless HTML_TOC flag

It's redundant. A zero `nesting_level` already means "disable TOC"
and a nonzero `nesting_level` enables it.

Having a TOC flag only complicates the code unnecessarily.
README: Remove incorrect statement

Anything can run out of memory, it's a normal thing.
What's important is to handle things correctly when
you run out of memory (i.e. don't crash).

Saying Hoedown will never run out of memory is
like saying dd-rescue will never get I/O errors.

I think the author meant "memory leak"
rather than "run out of memory".
Remove wrong grow()s in escape

They assume the buffer is empty, which is wrong.

Even if they took that into account, these small grows
are useless most of the time (the unit is big).
Simplify some code regarding fenced blocks
Merge branch 'master' into small-fixes
html: Remove SKIP_{STYLE,IMAGES,LINKS} flags (see #62)

Even with these flags active, injections and XSS are still easily possible.

Providing full attribute checking, HTML validation, ... is out of the
scope of Hoedown, therefore this "security" features only create
a false sense of security rather than actually providing it.
Revert .gitignore

This reverts commit b751c1708950292e96bd92e803a0db36b74f0b6b.
Merge pull request #72 from jmendeth/small-fixes

Small fixes
Allow custom memory allocation callbacks on buffer

Forked from txdv@memfuncs4, see #73 for discussion.