Added min/max functions

[muldereric]

Added getMin() and getMax() for a user of the library to easily keep
track of the lowest and highest value that were inserted in the
data-set.

[RobTillaart]

Thanks for this addition, I left those out of my original design to keep footprint minimal. Current compiler will optimize them out if not used, so I would like to add them.
However in case the _min and _max are both NAN the comparisons will produce false as wanted but comparing with NAN can be prevented which is imho more robust.

So I propose to change these lines

• if (f < _min) _min = f;
• if (f > _max) _max = f;
• if (_cnt == 0) _min = _max = f;

to

• if (_cnt == 0) _min = _max = f;
• else if (f < _min) _min = f;
• else if (f > _max) _max = f;

That will prevent comparing with NAN and reduce the average number of (float) compares.

[muldereric]

As mentioned and long over due, I moved the code up 2 lines :)

[RobTillaart]

Note getMin() and getMax() gives the minimum/maximum since last call to clear(),
==> so it is not the min/max of the internal buffer.

• refactored a bit to minimize footprint (0.2.08)
• fixed some typos