no need for separate in_data parameter

I've had this locally for a while.

Not sure if I like the change anymore since it adds 1 line :(

Also, it looks like if you are not using the output, `Kernel.system` may be more efficient in memory, per the example in the [ruby-doc][].
We'd probably use backticks, but doesn't look like it has the same security precautions since `;` can go through no problem.

It is also of note, that `Kernel.system("cmd", "arg1", "arg2")` properly escapes the parameters. Not sure if we can leverage what they are calling under the covers to do the escaping for us. (which is potentially more robust)

[ruby-doc]: http://ruby-doc.org/stdlib-1.9.3/libdoc/open3/rdoc/Open3.html#method-c-capture3