Multiple URLS about datadeps.jl HOT 1 CLOSED

This means when registering,
if one has multiple remote_paths (URLS, normally),
one would need a corresponding number of file hashes.
So perhaps, the signature should be:

RegisterDataDep(
 DataName #Unique name for this data, determines its foldername, and the name used to represent it in code
("http://www.example.com/eg1.zip",  md5"aa674eb1ffb744954a45f2460666b469"),
("http://www.example.com/eg2.zip",  md5"aaff22aa33aa44aa55ee444dddaaa4421"),
...
 ;
 fetch_method = download  
 post_fetch_method = unzip 
 extra_message ="""This is an extra message to be shown before downloading file"""

One also might want one fetch_method and post_fetch_method per entry, eg if some files are zipped and others are tarballed.
Its is an unusual case,
Probably skip it for now, then if it occurs can always add it as a feature later once someone raises an issue.
Probably implement it as allowing arguments to take a single function, or a tuple of functions (like MLDataUtils)

from datadeps.jl.