rm es6-set - shave 80% off browser build size, drop 0.10 and old browser support

[davidmarkclements]

browserify -r bloomrun | wc -c 
49671

after removal

browserify -r bloomrun | wc -c 
10987

Support for Set is from Node 0.12 and up, browser support is from ie11, safari 8, android 5.1, safari ios 8, and FF and chrome have had it for ages too

Support for for very old browsers can be in the users hands (just include a global es6 shim)

[mcollina]

You should probably remove node v0.10 from .travis.yml and bump the major.

@mcdonnelldean anything against this?

[mcdonnelldean]

@mcollina I'm good with this. I'll be dropping 0.10 off of Nanite.. But there may be other reasons not to....