[Ur] New release

[Adam Chlipala]

A new release is available at:
       https://github.com/urweb/urweb/releases/tag/20200209

CHANGELOG for this release:

- New invocation mode 'urweb daemon restart'
- Disallow wildcards in signatures
- At compile time, start allowing "#" as a URL
- New option '-u' for generated HTTP servers, to use UNIX sockets
- New HTML tag attribute: 'step' (for <crange>)
- New SQL function: 'similar' (via pg_trgm)
- New List function: foldli
- New Json functions: json_record_withOptional, json_time, rfc3339_in, 
rfc3339_out
- New Datetime member: ord_month
- New JavaScript FFI function 'listen'
- Experimental support for the Language Server Protocol (helpful for IDEs)
- Bug fixes and improvements to documentation, error messages, 
performance, and compatibility