Count min sketch

[aesteve]

Count-Min Sketch

Description

This is a first step towards adding more probabilistic data structures (like Bloom Filters for example).
This PR contains:

• a new probabilistic module under the data_structures one
• a CountMinSketch trait containing the contract (basically, increment & return count)
• the default implementation using multiple hash functions
• **the introduction of quickcheck as dependency for Property-Based-Testing` which:
  • is really relevant in the case of probabilistic data structures because we can't test exact behavior but rather a property (in that case, a CountMinSketch must not underestimate the count, only overestimate it)
  • would (I think) benefit a lot in other modules like sorting. Since what we want to test in a lot of implementation is the "Oracle" property (for instance in all the sort implementations, we can just generate random inputs and compare with Rust's sort function. This could greatly simplify the tests.

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• I ran bellow commands using the latest version of rust nightly.
• I ran cargo clippy --all -- -D warnings just before my last commit and fixed any issue that was found.
• I ran cargo fmt just before my last commit.
• I ran cargo test just before my last commit and all tests passed.
• I checked COUNTRIBUTING.md and my code follows its guidelines.

[siriak]

The code looks good, thanks!

[siriak]

Looks good, thanks!