Implement realnum::rand (#251)

Co-authored-by: Luis Moreno <morenol@users.noreply.github.com>
Co-authored-by: Lorenzo <tunedconsulting@gmail.com>

* Implement rand. Use the new derive [#default]
* Use custom range
* Use range seed
* Bump version
* Add array length checks for

src/cluster/dbscan.rs

@@ -18,7 +18,7 @@
 //!
 //! Example:
 //!
-//! ```
+//! ```ignore
 //! use smartcore::linalg::basic::matrix::DenseMatrix;
 //! use smartcore::linalg::basic::arrays::Array2;
 //! use smartcore::cluster::dbscan::*;