* Minor syntax highlight adjustments
- Highlight at-words in cyan instead of red.
- Highlight strings in green instead of red.
- Highlight punctuation in yellow instead of bold. (Uncolored bold does
not look very good on Ubuntu based systems.)
- Don't highlight the token at the error location with a red background.
The idea is to reserve red for errors, and sync with babel-code-frame.
Note that `()` are _not_ highlighted. Those characters are usually part
of a 'brackets' token, which is already highlighted. When they're not,
highlighting them did not improve the output.
Many text editor color schemes (and babel-code-frame) don't highlight
`{}[]`, because those characters are usually surrounded by other colored
tokens, which makes the output to noisy. However, that's not true for
postcss' syntax highlighter, so it makes sense to highlight those
characters.
* Add syntax highlighting for classes and hashes
Hashes refer to `#id` selectors and `#f50` colors.
* Add syntax highlighting for "calls"
Calls refer to the word before a 'brackets' or '(' token, such as in
`not(...)`, `rgb(0, 0, 0)` and `calc(...)`.
* Fix multiline tokens highlighting the line gutter
* Fix typo in test description in test/css-syntax-error.js
* Fix ^ position when highlighting code indented with tabs
Andrey Sitnik