implement tables
fix [0] reference labels
simplify content types
psr-2 names
Add set_breaks_enabled() as an alias for BC

Backwards-compatibility is kept with versions before PSR-2 naming.

See http://git.io/SsTarw
Merge pull request #124 from hkdobrev/psr-2-bc

Add set_breaks_enabled() as an alias for BC
Merge branch 'master' of https://github.com/erusev/parsedown