Fix #136; allow callable defaults
Fix broken test case
Update CHANGELOG.md
show the value rather than the lambda

Pre fix:
irb> class I < ActiveInteraction::Base
irb>   date :d, default: -> { Time.now }
irb>   def execute; d; end
irb> end
ActiveInteraction::InvalidDefaultError: d: #<Proc:0x007f8a5d0690c0@(irb):6 (lambda)>
Merge branch 'master' into default-procs

Conflicts:
	CHANGELOG.md
Use callable defaults in example
Complain if the hash inside a proc isn't empty
Extract default fetching and calling into private helper
DRY up hash defaults
Merge branch 'v1.1.0' into default-procs

Conflicts:
	CHANGELOG.md
Move default? check back into default
Merge pull request #141 from orgsync/default-procs

Allow callable defaults