Passing Popen args argument as list
Passing Popen args argument as list

On UNIX, command-line arguments cannot be used if the Popen args
argument is a string. This commit splits the command string into a
list of arguments.

Currently, calling the render method on a Digraph object causes an
OSError to be raised on UNIX systems. This commit fixes that.

ericfrederich/graphviz,xflr6/graphviz,gregelin/graphviz