Haml compatibility issues

[DrkCloudStrife]

This addresses the changes made in haml 5 where interpolated code is escaped by default unless escape_html and escape_attrs values are false. haml/haml#770

Additionally, even though haml doesn't seem to depend on tilt > 2, there is a dependency on Tilt::ErubiTemplate which was introduced in tilt 2. Hence loosen up of tilt gem.

Refs:

• https://github.com/haml/haml/blob/c757d9e9283e02cc1e7f26c0a8b3da05ec5cdc90/lib/haml/helpers/safe_erubi_template.rb#L13
• Add support for Erubi template engine for erb and rhtml files rtomayko/tilt#308