Crossing 0 longitude

[ryanreisinger]

When individuals cross 0 degree longitude, the estimated locations are at -180/+180 longitude.

Fix for #2 might have caused a new issue.

[lmsa.zip](https://github.com/ianjonsen/foieGras/files/2850289/lmsa.zip)

library(foieGras)
library(dplyr)

dat <- read.csv("lmsa.csv") #in zip file attached.

output <- foieGras::fit_ssm(d = select(dat, id, date, lc, lon, lat),
                            vmax = 36,
                            min.dt = 120,
                            time.step = 2)

plot(output$ssm[[1]], est = "predicted")

[ryanreisinger]

[ianjonsen]

I've uploaded a fix that works for this track and the previous example track crossing -180/180. I've also added a lonWrap argument to the plot method where user can specify a minimum longitude for wrapping: 0 to deal with dateline issue, or -180 to deal with crossing 0,360. The default is no wrapping.

I'll leave this issue open for now, in case you run into more problems