6.5.0: Optional mapper for array and map terminals

• Merged PR #36: Add optional mapper to toArray() and toMap() - @thekid

6.4.2: Deprecate concat()

• Merged PR #42: Deprecate static concat() in favor of multiple-argument
  of(). Also deprecates util.data.Iterators class.
  (@thekid)

6.4.1: Performance improvements

• Merged PR #41: Inline collecting() and counting(). Both methods are
  now four times faster.
  (@thekid)
• Heads up: Deprecated the following classes which were inlined:
  . AbstractMapper, Mapper, MapperWithKey
  . AbstractWindow, Window, WindowWithKey
  . AbstractFilterable, Filterable, FilterableWithKey
  . Flattener
  . Generator
  These will be removed in the next major release!
  (@thekid)
• Merged PR #40: Inline Generator class. Improves performance of the
  creation methods generate() and iterate() roughly three times.
  (@thekid)
• Merged PR #39: Inline intermediate operations using yield. This
  brings a performance improvement for filter(), map(), peek(),
  flatten(), skip() and limit() with factors ranging from 4.1
  up until 8.7 for the default cases; and double performance for both
  skip() and limit() with integer limits.
  (@thekid)

6.4.0: CannotReset exception

• Merged PR #35: Add util.data.CannotReset exception class replacing
  lang.IllegalStateException for indicating a sequence can't be processed
  more than once. This makes it easier to distinguish exception causes
  and handle them separately if necessary.
  (@thekid)

6.3.0: Flatten with yield

• Merged PR #34: Add ability to use yield statements inside flatten()
  (@thekid)

6.2.1: Limit fix

• Fixed issue with limit() closure being invoked with NULL when the
  end of the sequence is reached.
  (@thekid)

6.2.0: Distinct function

• Merged PR #33: Add optional "function" parameter to distinct() - @thekid

6.1.0: XP8 compatibility

• Added forward compatibility with XP 8.0.0 - @thekid

6.0.0: Drop PHP 5.5 support

• Merged PR #32: Drop PHP 5.5 support, use native varargs & unpacking
  (@thekid)

5.2.0: Find first

• Merged PR #31: Add optional filter to first() operation - @thekid