Prefer vim to vi for default editor (#4230)

* vim > vi
* Allow which to accept multiple args
* Update __init__ to use which with multiple args
* Fix doc tests

var/spack/repos/builtin/packages/hdf5/package.py

@@ -263,7 +263,7 @@ def check_install(self):
                  spec['hdf5'].libs.ld_flags.split()))
             try:
                 check = Executable('./check')
-                output = check(return_output=True)
+                output = check(output=str)
             except:
                 output = ""
             success = output == expected