Discourage use_ok in the docs.

[schwern]

use_ok is generally considered harmful, or at least unnecessary, if all is required is to load a module in a test. A simple use will work fine and will stop the test if it fails rather than trying to push on.

• Remove recommendations for use_ok just to load a module in the docs
• Recommend require_ok if a series of modules need to be loaded

[pdl]

#287 mentions that lexical effects were an addition. Test::More.pm currently states:

Lexical effects will occur as usual.  For example, this will turn on strictures.

  BEGIN { use_ok "strict"; }

However, these lines are not present in 0.98. Should these also be removed as part of this issue (or as part of #287?)

[schwern]

They should be removed as part of #287 which removes the lexical effect functionality. If it's easier to blur #287 and #288 that's fine.