fixed v0.4 error with function cat(..) by changing to concat

update subplot.jl cat -> concat

fixed for v0.4 errors

concat(..) -> Gadfly.Aesthetics.concat(..)

Pull from upstream/master
typo: Nev → Nov / make month abbrevs same length

typo: Nev → Nov / make month abbrevs same length

Pull from PR #502
Fix bounds for Date plotting in years

When plotting Dates in years, Gadfly previously chose x_max as the year of the maximum date.  This would truncate any data points that are in the most recent year after January 1.

This patch changes it to be the year of the maximum date plus a year less a day, retaining the current behavior for dates that fall exactly on January one, and choosing better bounds for all other dates.