Add the ability to specify cores per task for SLURM (#94)

* Addition of a general way to append additional parameters.

* Addition of "cores per task" to SLURM adapter.

maestrowf/interfaces/script/slurmscriptadapter.py

@@ -87,6 +87,7 @@ def __init__(self, **kwargs):
             "ntasks": "-n",
             "nodes": "-N",
             "reservation": "--reservation",
+            "cores per task": "-c",
         }
 
     def get_header(self, step):
@@ -140,12 +141,15 @@ def get_parallelize_command(self, procs, nodes=None, **kwargs):
                 str(nodes),
             ]
 
-        rsvp = kwargs.pop("reservation", "")
-        if rsvp:
-            args += [
-                self._cmd_flags["reservation"],
-                "\"{}\"".format(str(rsvp))
-            ]
+        for key, value in kwargs.items():
+            if key not in self._cmd_flags:
+                LOGGER.warning("'%s' is not supported -- ommitted.")
+                continue
+            if value:
+                args += [
+                    self._cmd_flags[key],
+                    "\"{}\"".format(str(value))
+                ]
 
         return " ".join(args)