Add expectations.  Rename formal parameter for consistency.  Organize with comments.
Support binary classification in bagEarth2sas.

Without specifying the class package in Suggests, the tests fail like this:
Running the tests in 'tests/test_sas.R' failed.
Last 13 lines of output:
  +     function(fit) { bagEarth2sas(fit, drop = FALSE) },
  +     test_bagEarth_predict)
  testing bagEarth_class from package caret
  changing working directory to:  C:/Users/aziem/AppData/Local/Temp
  fitting model
  earth glm subY: did not converge after 25 iterations
  earth glm subY: did not converge after 25 iterations
  earth glm subY: did not converge after 25 iterations
  Error in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()), versionCheck = vI[[j]]) :
    there is no package called 'class'
  Calls: test_foo2sas ... tryCatch -> tryCatchList -> tryCatchOne -> <Anonymous>
  In addition: There were 13 warnings (use warnings() to see them)
  Execution halted
Error: Command failed (1)
In addition: Warning message: