Refactor so sequence of operations is clearer and code cleaner
Refactor so sequence of operations is clearer and code cleaner

*   Split data gathering from string creation. Make sure we have
    all the data required by the template before we start
    trying to create the output zip file name.

*   Move the code for packing the zip file (packFiles()) and the
    code for getting the git commit (gitCommitId()) out of the main
    task definition and into private functions. This makes it easier
    to follow the code.

*   Use a template string for the zip file name. This is cleaner
    (it's clear how the data will be interpolated into the template
    string for the zip filename, as it's just a lodash template).

*   Files can be added to zip file in parallel.

    Can use async.each() rather than async.forEachSeries(), as the
order in which files are added to the output zipfile doesn't
matter.

    This might make creation of the zip file slightly faster (and
if it doesn't it doesn't matter anyway).

01org/grunt-zipup,pombreda/grunt-zipup