Clarify source of 2nd render pass re: preloading data
Clarify source of 2nd render pass re: preloading data

While the docs do say that a second render pass for preloaded data comes
from request completion, the example code for preloading data suggests that
a promise chain returned from `oninit` has a role to play in controlling the
second render pass.

The docs should make explicit where the redraw is initiated so the reader
does not mistakingly believe that `oninit()` retuning a promise changes
anything.

pygy/mithril.js,lhorie/mithril.js,impinball/mithril.js,MithrilJS/mithril.js,lhorie/mithril.js,barneycarroll/mithril.js,impinball/mithril.js,tivac/mithril.js,MithrilJS/mithril.js,pygy/mithril.js,tivac/mithril.js,barneycarroll/mithril.js