chore(gulp): add watcher
fixe(test): Update to gulp 3.0.0
file.shortened changed to file.relative
and file.path returns the absolute path
see https://github.com/wearefractal/gulp/blob/master/CHANGELOG.md#30
chore(test): add test of arguments to renaming function

Following https://github.com/hparra/gulp-rename/pull/1#issuecomment-29965795

For `hello.min.txt` I isolate 
 * the first name : `hello`
 * the base name : `hello.min`
 * keeping the extension : `.txt`