adding skip_trash option to remove method

Change-Id: I068f7b55230f14fc38c9a11957fd5387e33a2d8a
Reviewed-on: https://gerrit.spotify.net/gerrit/49220
TC-Compile-And-Test: Team City <teamcity@spotify.com>
Reviewed-by: Elias Freider <freider@spotify.com>

Conflicts:
	luigi/hdfs.py