Reboot

[jescalan]

Starting fresh. This first commit adds basic expression evaluation capabilities. Still to go:

• escape html characters in basic delimiters
• add unescaped delimiters
• add conditional statements
• add each loops

[michael-ciniawsky]

Please leave the README (header, headings center, license appended) for consistency

[jescalan]

@michael-ciniawsky We can discuss further in gitter if you want, but I'm not ok with centered headings, both for aesthetic and conventional purposes. No other repos center headings, and it breaks outside of github's default by overriding html with inline styles into markdown. The logo is aligned the same way it is in the primary posthtml repo, as well as sugarml and posthtml-content. Same with the license, there is no reason to append it to the readme -- it's duplication for no reason, and it's not this way in sugarml, content, or the primary posthtml repo.