support HR and headings as block markups
simple html cases
Merge pull request #110 from wkpark/hr_heading

support HTML hr and headings
fixup internal reference labling to make code more readable
Merge pull request #114 from wkpark/fixup_reference_label

fixup internal reference labling to make code more readable
parser should be less dependent on compiler
remove obsolete variables
arrange methods
move synopsis to the top
replace synopsis with a more appropriate word
simplify example
resolve #117
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
fixup regression due to commit 59907ff7 "simplify em/strong routine"

use $closestMarkerIndex correctly
Merge pull request #122 from wkpark/marker_index

use $closestMarkerIndex