Add new option to apply jshint to all file (not only html files which has script element).

This pull-req introduces a new option 'lintAllFile' (boolean, default: false). If this option is enabled, grunt-lint-inline applies jshint not only html files which contains script elements but also all file specified in Gruntfile.js.

The motivation is that I'd like to apply jshint both html and js file at once. Also would like to output result to one file. 

I guess it's better that lint target files are defined at config file (Gruntfile.js), not in a module. Because grunt-contrib-jshint does so (it applies jshint to all file specified in Gruntfile.js). Also we can write complex rule in Gruntfile.js by 'ignores' option or grunt globbing patterns such as '*', '!'.

For backward compatibility I added the option and disable it by default.

Thanks.