Node version (or tell us if you're using electron or some other framework):

7.5.0

ShellJS version (the most recent version/Github branch you see the bug on):

0.7.5

Operating system:

Mac OS X

Description of the bug:

If you try to copy a file to the folder it already belongs to, the content of the file is erased.

Example ShellJS command to reproduce the error:

echo "blah" > /home/test

shell.cp('/home/test', '/home')

cat /home/test

/home/test is now empty.