Use Javelin workflow on directory item deletion

Summary:
I think I wrote this before I laid in workflow, so they always redirect to
another page even if you have JS. Use workflow if it's available.

Test Plan:
Deleted a directory item and a directory category via dialog workflow instead of
full page reloads.

Reviewed By: jungejason
Reviewers: jungejason, tuomaspelkonen, aran
CC: moskov, aran, jungejason
Differential Revision: 359