v2.4.0

Notable changes

• bem-core dependency was updated to 2.8.0.
• Accessibility (a11y) was improved in all blocks (#1206).
• dist build is now uses bem-xjst@next, which gives possibility to add templates in runtime.

Other changes

• dropdown does not generate extra wrapper around switcher and popup any more (#1392).
• Misused <i> element replaced with neutral <span> in all blocks (#1668).
• Multiline comments in stylus files, which break source maps, replaced with singleline (#1702).