Extend blockquote on Enter at the end of the line
Fix: `Enter` doesn't remove _empty_ ordered list item if it's multi-digit
Disable some keybindings inside code blocks/spans

Some of them are related to `*`, `_`, `~`, `#`, `>`
Fix a README typo
Expand GFM tasks with `Enter`

Fixes #145
Improve symbol list definition for headers
Improve blockquote extending (via `Enter`)

Multilevel blockquotes weren't supported, now they are.
Reflect "Tips" wiki to the README
Convert selected text to blockquote with `>` key
Small fixes for blockquote extending
README update for 4a89b40
A small bugfix for converting to blockquote
Add C# support to fenced code blocks

Fixes #147
Merge branch 'v2.0.5'