Remove monkey patch for Lexer#number

The Sass parser's source map now gives us enough information to
implement the `LeadingZero` linter without requiring a monkey patch.

Remove the patch.

Change-Id: I112f6e108c2e8b66c8e01430ec767161f50dd813
Reviewed-on: http://gerrit.causes.com/36424
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Ignore FormatString cop

Using '%' is convenient when dealing with customizable strings.

Change-Id: I910dd5e5537245367eee7280dfc90b887b1ea286
Reviewed-on: http://gerrit.causes.com/36425
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>