plugins can be pluged in options

[paragraff]

Hi @coderhaoxin!
Markup for include files may be different in projects, not only @@include (). For example, in my project markup is like: /{file=some_file.html some_params=1}/, but markup if and variables can be used.
What if features add as plugin to gulp-file-include?
For example i use two plugins: https://github.com/paragraff/gulp-file-include-image-plugin and https://github.com/paragraff/gulp-file-include-script-fetch-plugin

[coveralls]

Coverage decreased (-1.0%) to 96.5% when pulling 8be0405 on paragraff:master into ff678de on coderhaoxin:master.

[haoxins]

Oh, a huge change.
I'll review it this weekend. 😄

[paragraff]

Thanks!