Changes in version 0.3.1

Added highlighting of:

incomplete sudo commands (a3047a9121, 2f05620b19)
```
  sudo;
  sudo -u;
```
command words following reserved words (#207, #222, b397b12ac1 et seq, 6fbd2aa957 et seq, 8b4adbd991)
```
  if ls; then ls; else ls; fi
  repeat 10 do ls; done
```
(The ls are now highlighted as a command.)
comments (when INTERACTIVE_COMMENTS is set) (#163, #167, 693de99a90)
```
  echo Hello # comment
```
closing brackets of arithmetic expansion, subshells, and blocks (#226, a59f442d2d, et seq)
```
  (( foo ))
  ( foo )
  { foo }
```

precommand modifiers at non-command-word position (#209, 2c9f8c8c95)
```
  ls command foo
```
sudo commands with infix redirections (#221, be006aded5, 86e9249709)
```
  sudo -u >/tmp/foo.out user ls
```
subshells; anonymous functions (#166, #194, 0d1bfbcbfa, 9e178f9f39)
```
  (true)
  () { true }
```
parameter assignment statements with no command (#205, 01d7eeb3c7)
```
  A=1;
```
(The semicolon used to be highlighted as a mistake)

main highlighter refactored to use states rather than booleans. (2080a441ac, et seq)
Fix initialization when sourcing zsh-syntax-highlighting.zsh via a symlink (083c47b007)
docs: Add screenshot. (57624bb9f6)
widgets wrapping: Don't add '--' when invoking widgets. (c808d2187a)
Refresh highlighting upon accept-* widgets (accept-line et al). (59fbdda64c)
Stop leaking match/mbegin/mend to global scope (thanks to upstream WARN_CREATE_GLOBAL improvements). (d3deffbf46)

Test harness converted to TAP format (d99aa58aaa, et seq)
Run each test in a separate subprocess, isolating them from each other (d99aa58aaa, et seq)
Fix test failure with nonexisting $HOME (#216, b2ac98b981)
Test output is now colorized. (4d3da30f8b, 6fe07c0961)
Document make install (a18a7427fd)
tests: Allow specifying the zsh binary to use. (557bb7e0c6)
tests: Add 'make perf' target (4513eaea71)

suffix aliases (requires zsh 5.1.1 or newer):
```
  alias -s png=display
  foo.png
```
prefix redirections:
```
  <foo.txt cat
```
redirection operators:
```
  echo > foo.txt
```
arithmetic evaluations:
```
  (( 42 ))
```
$'' strings, including \x/\octal/\u/\U escapes
```
  : $'foo\u0040bar'
```
multiline strings:
```
  % echo "line 1
  line 2"
```
string literals that haven't been finished:
```
  % echo "Hello, world
```
command words that involve tilde expansion:
```
  % ~/bin/foo
```

quoted command words:
```
  % \ls
```
backslash escapes in "" strings:
```
  % echo "\x41"
```
noglob after command separator:
```
  % :; noglob echo *
```
glob after command separator, when the first command starts with 'noglob':
```
  % noglob true; echo *
```
the region (vi visual mode / set-mark-command) (issue #165)
redirection and command separators that would be highlighted as path_approx
```
  % echo foo;‸
  % echo <‸
```
(where ‸ represents the cursor location)
escaped globbing (outside quotes)
```
  % echo \*
```

(Start of changelog.)