Multiple images inlining now works

[akzhan]

Now gulp-juice correctly inline multiple images and depends on actual version of juice.

P.S.: Closes #5, #6 and #8.

P.P.S.: Now available as premailer-gulp-juice npm package.

[akzhan]

I recommend to release it as 0.1.4 to follow juice 4.

[alenvuletic]

@imlucas Please can you merge this into master and create new release?

Thanks!