Add utility to animate outputs

[mikejohnson51]

Add gifski as a dependency to provide animation tools.

animate = function(data, ...) {

...
}

[mikejohnson51]

We now have

AOI = AOI::aoi_get(state = "OR")

g = getGLDAS(AOI = AOI,
         varname='rootmoist_inst',
         model='NOAH025_M.2.1',
         startDate='2006-10-01',
         endDate='2007-09-30')

animation(g$rootmoist_inst, 
          AOI = AOI,
          outfile = "tester.gif")

[mikejohnson51]

Added vector animation capacity:

AOI = AOI::aoi_get(state = "south", county = "all")

getGridMET(AOI,
               varname = "pr",
               startDate = "1991-10-29",
               endDate  = "1991-11-06") %>% 
  execute_zonal(geom = AOI, ID = "fip_code") %>% 
  animation(feild_pattern = "pr_", outfile = "test.gif")

[mikejohnson51]

@anguswg-ucsb would you mind reviewing this changes (in viz.R) and seeing what you'd change/improve?

[anguswg-ucsb]

@anguswg-ucsb would you mind reviewing this changes (in viz.R) and seeing what you'd change/improve?

Yes, I'll take a look and let you know my edits.

[mikejohnson51]

Super! If you find/add anything please send it this way as a PR :)