v4.2.0

Bug Fixes

• better empty heading check, #34, #36, #45 (00ddf0b)
• remove potential infinite loop, DDOS vector (1e55cc1)
• restore class methods on Token objects (b1b8855)
• change typography option to typographer, #38, thanks cesalberca
• nested anchors support, #46, thanks watagashi

Features

• add anchorLinkPrefix option #27, thanks ruanyf
• add wrapHeadingTextInAnchor option #28, thanks jsepia
• add slugify option, improve example in README, add corresponding test (a085aaf)