Added 'chunk' method.

Added 'chunk' method to query builder and Eloquent for doing work on
large result sets.
merge 4.0.
work on merging 4.0 branch.
Do strict check on MAC.
Merge remote-tracking branch 'origin/4.0'
integrate Boris into Tinker command hwen available.
update change log.
tweak composer layout.
simplify prompt.
Fix "slow Redirect".