Corrected node.js version requirement.

package.json was being told that nodebb only required version >=0.8.x of node. Per documentation and communication with developers this should be >=0.10.x
Changing this should help users who accidentally run nodebb on node.js 0.8 to run it on a supported version of 0.10.x or highter.
removed off from search button
fixed ip:recent weird
same deal as previous commit
closes #1978
closes #1978
fixed #1980 -- missing pass-through
possible fix for #1981
small optimizations

user.isOnline works with an array of uids
do not make 2 trips to db to get main post and first 10 posts
send uids to isOnline in messaging
crash fix
reverted main post change, breaks indices
doing it properly this time

mainPost always has index 0
further fix to #1957
sacrificing a goat to ensure this doesn't come back to bite me
fixed #1981
fix isSortedSetMembers on mongo
check mainPid
added uid to filter:header.build
fixed #1988