Avoid spurious warning when loaded before ido.

Normally ido-ubiquitous warns you if you enable it without first
enabling ido. However, this can cause spurious warnings during init if
ido-ubiquitous is loaded first. As a solution, during init we now use
"after-init-hook" to only warn if ido still isn't enabled when init is
complete. After init, behavior is unchanged.
Version 1.7