C++17 standard + higher optimizations in Release build

[aminya]

Requires #88

Description of the change

This PR adds a release configuration (as the default configuration) that:

• Uses C++17 standard
• Uses higher compiler optimizations

Benefits

• Newer C++ standard allows using better algorithms, optimizations, and better defaults in general. In future PRs, we can make use of C++17 features such as built-in optional support.
• Higher compiler optimizations instruct the compilers to work hard for optimizing the code. This results in higher performance

Verifications

The tests pass.

Release Notes

• Uses C++17 standard
• Uses higher compiler optimizations

[aminya]

Travis is truly broken. I can't install clang on it (tried clang 10 and 9). I would merge #88 to fix all the CI issues instead of trying to fix Travis.