[ALOY-249] Better error output on python < 2.7

Right now error output from the Titanium compiler plugin only lists the alloy error output if python 2.7+ is installed. Otherwise it defers to an older method of output that doesn't give all the information. We need someone with python chops to make a fix here so that we can get good error logs regardless of the version of python installed, so long as that version meets the minimum standards for Titanium, which I believe is 2.6+. Changes need to be made here: https://github.com/appcelerator/alloy/blob/master/Alloy/plugin/plugin.py From original ticket: The subprocess.check_output method is currently used by the ti.alloy compiler plugin to execute the appropriate commands and output error information, if necessary. While this works well and gives us good error logs, it only works for python 2.7+, where in its current state, Titanium supports 2.6+. There is a fallback function that is executed in case the developer does not have 2.7+ installed, subprocess.check_call. This method, unfortunately, does not give the full error log subprocess.check_output does. We need to implement a method in the ti.alloy compiler plugin that allows for solid error output on python 2.6+.