When calculating array indexes from hash, value must be positive

Since % in c# preserves the negative sign if the first operand is
negative, e.g. -5 % 2 -->-1, so we need to make sure it's positive
Merge pull request #195 from HCanber/positive-routees-index

Fixes ConsistentHashingRoutingLogic index calculation
The hash value can be negative, and % in C# preserves the 
negative sign if the first operand (i.e. the hash value) is negative.
e.g. -5 % 2 --> -1
So we need to make sure it's always positive