support @noflipStart-@noflipEnd to protect multiple rules

Tests and docs included.
Fixes #28

I got some lint errors from jscs. I also got them on the master branch so I ignore them for now. If the travis build will fail I'll submit another commit to fix them.
```
Running "jscs:all" (jscs) task
Invalid line break at Gruntfile.js :
     1 |module.exports = function ( grunt ) {
---------------------------------------------^
     2 | grunt.loadNpmTasks( 'grunt-contrib-jshint' );
     3 | grunt.loadNpmTasks( 'grunt-contrib-watch' );
Invalid line break at build/tasks/unit.js :
     1 |module.exports = function ( grunt ) {
---------------------------------------------^
     2 | grunt.registerTask( 'unit', function () {
     3 |  var assert = require( 'assert' ),
Invalid line break at src/cssjanus.js :
     1 |/*!
-----------^
     2 | * Converts CSS stylesheets between left-to-right and right-to-left.
     3 | * https://github.com/cssjanus/cssjanus
Multiple line break at src/cssjanus.js :
   252 |    noFlipMultipleTokenizer = new Tokenizer( noFlipMultipleRegExp,  noFlipMultipleToken ),
   253 |    commentTokenizer = new Tokenizer( commentRegExp, commentToken );
   254 |
--------^
   255 |
   256 |   // Tokenize
>> 4 code style errors found!
Warning: Task "jscs:all" failed. Use --force to continue.
```