#4 add test module

 add test module.
 add requirement to nose for test.
 #17 add delete line magic
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 when I want to delete collection or db in mongo. use %delete line magic.
 - %delete db.collection : delete collection
 - %delete db : delete db

 I will make delete_data line magic.
 this function matched by conn.drop_database() and conn.db.drop_collections('name') in pymongo.