Improve code efficiency of max(), maxBy(), min(), minBy(), minmax(),
minmaxBy()
Improve code coverage
Improve code style
Improve code coverage
Trim code
Improve code of groupBy() & sortBy()
Lazy loading first peek of PeekingIterator
Improve code coverage & code style
Add RubyFile::size & RubyFile::expandPath(file, dir)
Improve code coverage
Improve code style
Improve code coverage
Fix the remove logic of StepIterator
Improve code coverage
Inprove code coverage
Update release-notes and README.md
Trim code
Lazy loading ReverseEachIterator#hasNext
Defensive copies are made while constructing CombinationIterator,
PermutationIterator, RepeatedCombinationIterator,
RepeatedPermutationIterator, ProductIterator and ZipIterator
Remove useless code