Fixed required arrays when parsing operation variables

[jeggy]

Defining variables that either have an array or required array, didn't get parsed correctly. This fixes both $ids: [Int] and $ids: [Int!]!

[coveralls]

Coverage increased (+0.2%) to 88.095% when pulling 1c625066f7752ffadb3b16dba78372d2ca47e1d9 on jeggy:fix-required-variable-arrays into 42fef4a82c722d8b8944ceef8d8801ee9d7ed23b on pgutkowski:master.