implement 'useCI' or similar to set up basic .travis file for automated module testing

[achubaty]

see here for getting travis setup for non-R packge code.

We would need to:

1. install any system dependencies (GDAL, mapshaper, etc.); [to be done by the user]
2. install all dependency packages (start with SpaDES and testthat, then parse the module metadata for reqdPkgs and install them);
3. ensure the template test .R files each load any packages required of them and clean up after themselves.

[eliotmcintire]

@achubaty Is this done?

[achubaty]

No. Automating this will be too tricky and it depends on the user setting up travis and GHA, etc. and dealing with system dependencies. (made easier using the mechanisms in place for GHA).

Since I'm doing this for several modules already, I should put this info in vignette instead so the user knows how to do it.

[achubaty]

@eliotmcintire Apparently it's partially implemented in b42eeef.

Reviewing now. Did you end up removing usethis from Suggests, because I am using it for this.