use Array.isArray() not instanceof Array
Merge pull request #105 from DanielBarnes/master

Consistent usage of Array.isArray()
with/without changes + tests
Merge pull request #109 from wpreul/master

Separating messages into external resources and documenting change
cache args length, and utils.assert
fix the broken thing
Merge pull request #108 from DanielBarnes/master

with/without changes + tests
Merge branch 'master' of github.com:spumko/joi

Merging upstream