hostnames

[zeke]

This PR adds a module and CLI for listing all hostnames by package count. Here are the top 30.

cc @juliangruber

Hostname	Packages
github.com	452768
bitbucket.org	553
git.oschina.net	219
gitlab.com	116
git.coding.net	114
archive.voodoowarez.com	81
gitee.com	60
gitlab.baidu.com	49
git-wip-us.apache.org	38
gitlab.alibaba-inc.com	36
npmjs.com	34
gitlab.imginconline.com	32
gitlab.coko.foundation	29
git.cryto.net	28
github.ibm.com	27
git.code.oa.com	24
vehicleregistrationapi.com	22
coding.net	21
gist.github.com	21
bitbucket.com	21
test.git	21
gitlab.soft-artel.com	20
baidu.com	19
archive.eldergods.com	18
registry.npmjs.org	18
hub.jazz.net	17
repo.eecs.berkeley.edu	16
gitlord.com	16
dev.incardata.com.cn	15
gitlab.58corp.com	15