Add a hashtable with cuckoo hashing algorithm

[Boiarshinov]

Add a hashtable with cuckoo hashing algorithm.
There is no implementation of that data structure here yet.

Could be a good first issue.

[haeshed]

Hey,
Added the implementation for Cuckoo Hashing, using a single (not double) table.
This is my first contribution so hopefully will be according to standards.
Just realized that I didn't ask to be assigned, will that be a problem?

Im open for criticism and/or changes to the code.
Thank you.

[haeshed]

Finished and merged.
Can close issue.