Handle more than 1000 entries

[nijotz]

You can't activate the contentful_middleman extension multiple times to get more than 1000 entries, because it will remove the existing YAML files. I had to modify contentful_middleman to allow more than 1000 entries:
https://github.com/Instrument/contentful_middleman/commit/c0313de2fecc70e7d27dbab52bbd9b61196dca6f

[neonichu]

Would be cool if you could make a PR out of that commit :)

[nijotz]

Thanks @dlitvakb!