Rainflow

Changed
- (68, 70) Dropped support for Python 2.7 and 3.6.
- (66) `importlib.metadata` no longer used to evaluate `rainflow.__version__`.

Fixed

- (62) Due to floating point accuracy `count_cycles` sometimes returned
more bins than what was specified by argument `nbins`. Thank you
[Kyle6699](https://github.com/Kyle6699) for reporting the bug and
providing a test case.

Changed
- (56) `extract_cycles` now returns no cycles for very short time series
(containing zero or one reversals). Contributed by
[denis-jasselette-jc](https://github.com/denis-jasselette-jc).
- (57) Dropped tests for Python 3.4 and 3.5 due to the extra work required
to make the CI and tests work for these old versions.

Fixed

- (48) Fixed a bug which caused some bins to appear twice, with counts
distributed randomly between the two.
Contributed by [CWE0](https://github.com/CWE0).

Changed
- (35) By default, the first and the last points in the time series
are treated as reversals.
- (37) Function `reversals` now yields index and value of each reversal,
instead of value only.
- (38) Function `extract_cycles` now yields range, mean, count, start index and
end index for each cycle instead of low, high and count.
- (43) Arguments `binsize` and `nbins` to `count_cycles` produce bins which
include the right edge and exclude the left edge.

Removed
- (35) Removed optional arguments `left` and `right` to functions
`reversals`, `extract_cycles` and `count_cycles`. The new behaviour
correspods to `left=True` and `right=True`.

Added
- (22) Function `count_cycles` now accepts optional arguments `binsize` and `nbins`
for binning cycle ranges. Contributed by [gsokoll](https://github.com/gsokoll).