Added Request module with HEAD support
Now uses HEAD requests to check for app manifests
watch position for changes when user says to use 'current' position
ensure provider constructed before notifying about changes; but do nothing on cancel
consistentize names; remove nonexistent nsIFakeListener reference
Updated request copy to reflect changes from SDK

Specifically refactored out an unnecessary function call
remove expired receipt option Issue #497
update watcher after timeout like nsGeolocation expects; excise cruft; update naming
correct name of nsGeolocationService in comment
add bkase to list of contributors
Merge pull request #551 from nickdesaulniers/remove_expired

remove expired receipt option Issue #497
Merge pull request #544 from mykmelez/watch-geolocation