Task:
- Implementing of the simple interface, using Java 7 and Java 8 approaches.
- Java7Aggregator – should use Java 7 approach to solve the problem (no packages from Java 8)
- Java8Aggregator – should use Java 8 Stream API to solve the problem
- Java8ParallelAggregator – should use parallel streams from Java 8 Stream API to solve the problem
- Java7ParallelAggregator -  use Java 7 approach to do parallel tasks (e.g. you may use fork/join framework) to solve the problem

Tests used to verify the task
- Use 'com.epam.cdp.m2.hw2.aggregator.suits' package to run test by implementation;
- Use classes inside 'com.epam.cdp.m2.hw2.aggregator.[sum|duplicates|frequency].impl' package to test each separate method of each separate implementation.