Enable array_forget to unset one or many keys
Add keyBy method to Collection
Merge pull request #4723 from lucasmichot/array-forget-many

Array forget many
Fix return type.
A fix for #4498 and #4684. Eloquent model now boots all used traits, not only those declared in current class only.
Cleaning up code. Fixing stuff. Tests.
Fixed collection docblocks
Add contains method to base collection
Fix order of methods.
Fix conflicts. Merge.