message: changelog: update for next release
diff: +TBD
  +===
  +This release includes a ground-up rewrite of the regex-syntax crate, which has
  +been in development for over a year.
  +
  +New features:
  +
  +* Error messages for invalid regexes have been greatly improved. You get these
  + automatically; you don't need to do anything. In addition to better
  + formatting, error messages will now explicitly call out the use of look
  + around. When regex 1.0 is released, this will happen for backreferences as
  + well.
  +* Full support for intersection, difference and symmetric difference of
  + character classes. These can be used via the `&&`, `--` and `~~` binary
  + operators within classes.
  +* A Unicode Level 1 conformat implementation of `\p{..}` character classes.
  + Things like `\p{scx:Hira}`, `\p{age:3.2}` or `\p{Changes_When_Casefolded}`
  + now work. All property name and value aliases are supported, and properties
  + are selected via loose matching. e.g., `\p{Greek}` is the same as
  + `\p{G r E e K}`.
  +* A new `UNICODE.md` document has been added to this repository that
  + exhaustively documents support for UTS#18.
  +* Empty sub-expressions are now permitted in most places. That is, `()+` is
  + now a valid regex.
  +* Almost everything in regex-syntax now uses constant stack space, even when
  + performing anaylsis that requires structural induction. This reduces the risk
  + of a user provided regular expression causing a stack overflow.
  +* [FEATURE #174](https://github.com/rust-lang/regex/issues/174):
  + The `Ast` type in `regex-syntax` now contains span information.
  +* [FEATURE #424](https://github.com/rust-lang/regex/issues/424):
  + Support `\u`, `\u{...}`, `\U` and `\U{...}` syntax for specifying code points
  + in a regular expression.
  +
  +
  0.2.6 (2018-02-08)
  ==================
  Bug fixes:
  