Support auto-correction in many space related cops.

For #553.
Fix bug in SpaceAroundOperators making it report tabs as missing space.
Skip auto-correction in some conflict cases.

Stop auto-correction in HashSyntax if it creates illegal code. Correction of `{:a=>1}` by both HashSyntax and SpaceAroundOperators destroys the code.

Bail out of TrailingBlankLines auto-correction if there are also TrailingWhitespace offences in those lines.

Bail out of MethodCallParentheses auto-correction if the call is going to be auto-corrected by EmptyLiteral.