add hooks to patch both the pre/post initialized instance
fix tiny infinite loop bug
move patch hook to loader instantiation time

This hook needs to happen earlier if we want to capture all the work
that loader does during instantiation.
remove yui instance hook as it's not currently useful
expect a single patch instead of an array of patches
use a better name for the hook and pass the config
unit test for loader hook
invoke doBeforeLoader after setting `this.context`
mention the loader hook in the documentation
Merge branch 'perf-hooks-instantiation' into dev-master

hook to patch loader during YUI instance initialization