Swarmlib

Changed
* cuckoo search: Ensure each nest is assigned a cuckoo position in the update step

[All Changes](https://github.com/HaaLeo/swarmlib/compare/v0.6.0...v0.6.1)

Changed
* the visualization of the _firefly algorithm_ and the _cuckoo search_. Now they both include velocities.
* the firefly algorithm including its API. Now it replays the same problem if `--continuous` is set.
* the `--continuous` flag. It requires no parameter anymore.
* the `--two-opt` flag. It requires no parameter anymore.

[All Changes](https://github.com/HaaLeo/swarmlib/compare/v0.5.0...v0.6.0)

Added
* a feature that performs _particle swarm optimization_ for one of the provided 2D functions. After each step the intermediate solution is plotted.

Changed
* the API. Now the classes `*Problem` can be directly imported from the `swarmlib` module.

[All Changes](https://github.com/HaaLeo/swarmlib/compare/v0.4.1...v0.5.0)

Changed
* pypi tags to enhance the package's discoverability.

[All Changes](https://github.com/HaaLeo/swarmlib/compare/v0.4.0...v0.4.1)

Added
* a feature that enables the _cuckoo search_ for one of the provided 2D functions. After each step the intermediate solution is plotted.

[All Changes](https://github.com/HaaLeo/swarmlib/compare/v0.3.2...v0.4.0)

Fixed
* a bug in the firefly algorithm that caused the application to crash when the ackley function was selected.

[All Changes](https://github.com/HaaLeo/swarmlib/compare/v0.3.1...v0.3.2)