add sanic app module documentations
add sanic app module documentations

Signed-off-by: Harsha Narayana <72913e58b13780640e11366724061cd83a01715c@gmail.com>

ashleysommer/sanic,yunstanford/sanic,channelcat/sanic,channelcat/sanic,yunstanford/sanic,lixxu/sanic,lixxu/sanic,ashleysommer/sanic,ashleysommer/sanic,yunstanford/sanic,lixxu/sanic,channelcat/sanic,lixxu/sanic,yunstanford/sanic,channelcat/sanic