Update for dplyr use
First changes to use data.frame and dplyr
Changes for using data.frame and dplyr
Testing code update for dplyr & data.frame changes
Code updates for using dplyr & data.frame
Tweaks
Suppress stupid NOTEs from R CMD CHECK
Minimum R version to 3.1
worldPlot to unused for now
Test fixes
Data frame holds NAs for non-existent dimensions

Changed cmip5data(), loadCMIP5(), testing code, so that non-existent
dimensions are recorded as NA in the `val` data frame. This is clearer
and saves significant memory.
Vignette update re removal of worldPlot
Make sure summary sees stat and filter functions
Added drop parameter to as.array.cmip5data
Documentation update
Changed checkTimePeriod() to not use ddply

This actually makes for a bit clunkier code…but it's the only
dependency on `plyr` in the entire code now, so worth it to remove.
Handle dimension-double-dispatch issue

I.e., when x[i,j,t] and lon[i], lat[j] give actual values. Addresses
issue #96 (although this may not be the permanent fix we want).
Update DESCRIPTION
Update loadCMIP5.R

Don't pass control directly to loadEnsemble
loadCMIP5 now honors ensemble parameter