fixes for WP Coding Guidelines
add for remote upgrade processes (props @SLv99)

Hopefully this will fix renaming issues when upgrading from remote services such as MainWP, ManageWP, InfiniteWP and iThemes Sync
check $upgrader instead of $_GET['action']

Check only fails if both are FALSE
switch plugin loads classes after plugins_loaded

Hopefully this fixes some of the issues with remote updaters like iThemes Sync, MainWP, InfiniteWP and ManageWP
instantiate updaters from main class

This was done to be able to instantiate during plugins_loaded so it plays nice with remote updaters.
cleanup commented code
remove is_admin check
remove $priority
change to init hook
bump
move init hook back to main plugin file
directly call class method
oops
forgot to make static
cleanup and finalize instantiation via init hook

Need to instantiate plugin and theme objects via init hook so remote services (ManageWP, InfiniteWP, MainWP, iThemes Sync, etc) will use plugin's updating functions.
Merge branch 'develop'