Add `@idata(iterable)` decorator-function.

The purpose is to avoid:: 

  @data(*[a for a in foo if a > 0])

ddt.py

@@ -58,9 +58,19 @@ def data(*values):
 
     Should be added to methods of instances of ``unittest.TestCase``.
 
+    """
+    return idata(values)
+
+
+def idata(iterable):
+    """
+    Method decorator to add to your test methods.
+
+    Should be added to methods of instances of ``unittest.TestCase``.
+
     """
     def wrapper(func):
-        setattr(func, DATA_ATTR, values)
+        setattr(func, DATA_ATTR, iterable)
         return func
     return wrapper