Update installation/download.html for 1.7.2
Merge pull request #671 from kenjis/fix_download

Update installation/download.html for 1.7.2
Updated parameter descriptions and added an example of using Mongo over a UNIX socket

Signed-off-by: Jim Ciallella <jimc@orangecoat.com>
Merge pull request #672 from allella/mongo-socket

Updated param descriptions and added example Mongo over UNIX Sockets
本家変更分をmerge