Dir.home is not implemented in Opal
Requires libraries statically when running Opal engine
Remove unsupported syntax to make Asciidoctor compatible with Opal
Encoding.default_external does not exist in Opal
Add toSet method for Array class when running Opal engine
Absolute reference for SUBS attribute
Requires kernel module to resolve warn method when running Opal engine
Explicit call on Kernel.warn method
Remove require kernel
Dir.home is not implemented in Opal
Encoding.default_external does not exist in Opal
Revert "Explicit call on Kernel.warn method"

This reverts commit 4c68998f6608f3c62f8237ebfdab3841ea36e528.
HACK: comment out warn method
WIP HTML5 Backends
WIP Immutable String replace gsub! by gsub + assignment
WIP bad New line
Move lock_in_subs method to Substituters module

Conflicts:

	lib/asciidoctor/abstract_block.rb
Fix require
Revert "Remove unsupported syntax to make Asciidoctor compatible with Opal"

This reverts commit 33178e7e565d2d9e92467ca603da7db5c3e019dc.
Add HTML5 backends as submodule

Conflicts:

	lib/asciidoctor.rb
	lib/asciidoctor/renderer.rb