Implement Enum.equal? with equality callback
Handle exit messages from tests in ex_unit

Fixes #982
Implement Keyword.delete_first, closes #984
Implement Dict.equal?
Merge pull request #985 from ericmj/exunit_exit

Handle exit messages from tests in ex_unit
Merge pull request #986 from meh/keyword-delete_first

Implement Keyword.delete_first
Merge pull request #980 from meh/dict-equal

Implement Dict.equal?
Return early in Dict.equal? if the dicts have different size
Merge pull request #988 from meh/dict-equal

Return early in Dict.equal? if the dicts have different size
Return nil from import
Clean up conversion to list
Ensure imports are passed around arg by arg, closes #990
Calculate target just once
Merge pull request #983 from meh/enum-equal

More Enum.equal? stuff
Define missing Kernel functions
Use monitors instead of links in exunit
Add more documentation to ExUnit.Callbacks
Remove short paths on Enum

They basically cost one local function call and
are rarely used (just when both iterators are empty)
Implement Enum.member?
Merge pull request #991 from ericmj/exunit_exit

Use monitors in ExUnit and document callbacks