Cmis.preferences.get: Addressed 'anonymous function does not always return a value' warnings.
nsIDownloadManager was deprecated as of FF26. This commit
updates Cmis.io.save() to deal with browsers newer than 26.0a1.

Resolves #51.
Make sure that directoryList actually parses correctly. If
there are any issues CMIS will prompt the user.

Resolves #50.
Remove dom window load event listener once it has fired. This resolves #49.
FF builds 26.0a1+ now use Downloads.jsm instead of nsIDownloadManager. This resolves #51.
Updated em:version and em:maxVersion