Using _ properly on server

[s7dhansh]

Based on this comment meteor/meteor#9276 (comment)

underscore must be provided on the server too in package.js.

@aslagle I am not raising a PR, as probably this is a good time to also import _ properly (or maybe remove it altogether), in all the files.

The error is (in case someone searches here), when meteor shell is running:

TypeError: Cannot read property 'isFunction' of undefined

[aslagle]

Fixed in 0.8.43. I fixed the dependency and republished, but it could probably be removed entirely on the server at least if you wanted to open a PR for that.