CSS: fix parsing custom identifier tokens, such as --0

Merge pull request #126 from mjethani/feature/css-layers

CSS: support layer at-rule

Refactor BinaryReader

JS: support import.meta expressions

Set minimum Go version to 1.11

HTML: fix template tags starting with <

HTML: return text and template tokens separately in lexer

Update dependencies

Decode UTF-8 properly from URLs

Fix replaceEntities