Lsga

Date: 2018-10-25
1. Make MPIUtil a singleton and remove in-module instantiation.
2. Standardize docstring for Sphinx documentation

Date: 2018-01-30
1. Fixed important bugs in individual clone.

Date: 2018-01-15
1. Removed redundant calling of fitness function in iteration.
2. Improved the efficiency.

Date: 2017-12-15
1. Removed verboisty parameter for `BinaryIndividual` class.
2. Added unittest for decimal individual.

Date: 2017-12-13
1. Added `DecimalIndividual` class.
2. Added decimal encoding individual support for flip bit mutation classes.
3. Fixed some bugs.

Date: 2017-12-12
1. Changed class names:
- `GAIndividual` -> `BinaryIndividual`
- `GAPopulation` -> `Population`
- `GASelection` -> `Selection`
- `GACrossover` -> `Crossover`
- `GAMutation` -> `Mutation`
- `variants` -> `solution`

2. Added abstract Individual base class `IndividualBase`:
- Users can inherit the `IndividualBase` class and add implementations of `encode` and `decode` methods to define you own custom individual class with different encoding methods.