Removed `"-*-user-select"` checks.

MDN precisely states that "user-select" is not a standard property.
https://developer.mozilla.org/en-US/docs/Web/CSS/user-select
Closes gh-385
"selector-newline": look for newline characters in selectors

Usually it's a forgotten comma, not a descendant combinator.
Closes gh-282
Update JSHint rules.
Enable JSHint's `indent` rule.
Enable JSHint's `quotmark` rule.
Enable JSHint's `eqeqeq` rule and remove `eqnull`.
Move global config to jshint's configuration.
Remove unused variables.
Enable strict mode.