2.3.0: Algebra & Random improvements

What's Changed

New Features

• Added Vector<Scalar> type (#110).
• Added diagonal/eye/identity & closure initializers to Matrix<Scalar> (#111, #134).
• Added shape property to Matrix<Scalar> (#152).
• Added variance function (#133).
• Added random/randomNormal functions for efficiently generating batches of random values (#154, #156).

Maintenance

• Migrated project to use Swift 5 (#97).
• Improved project documentation in README file (#103, #112, #115, …).
• Greatly improved project's unit test suite (#104, #108, #110, #118, #119, #120, #122, #127, #129).
• Added a benchmark suite (#123, #126).
• Cleaned up project structure and implementation (#97, #103, #109, #114, #116, #118, #142).