do not raise an IncompatibleOptionValues For a couple of potentially valid use cases

[jeradphelps]

I believe the following two params blocks should be valid:

# The default is the entire range of allowed values
params { optional :numbers, type: Array[Integer], values: 0..2, default: 0..2 }

# The default is a subset of the entire range of allowed values
subject.params { optional :numbers, type: Array[Integer], values: [0, 1, 2], default: [1, 0] }

The current implementation doesn't account for these use cases and raises Grape::Exceptions::IncompatibleOptionValues. This PR will allow the two cases above.

[dblock]

Looks good! 👍