Fixed installation via composer

Hi,

Just checking out your module, and found a couple of issues with the composer/modman installation:
* Composer was complaining that composer.json wasn't valid JSON (nneeds double quotes instead of single quotes)
* The modman file referred to a setup script (app/code/community/Demac/MultiLocationInventory/sql/demac_multilocationinventory_setup/upgrade-1.1.6-1.1.7.php) that no longer exists.

The two commits in this pull request fix both of those issues.  Once this is done, I was able to install the module successfully with composer.