Rename modulo to remainder and add examples

[cousteaulecommandant]

First, the Arduino reference refers to % as "modulo". However "remainder" is a more appropriate (and familiar) name (and the one used in the C++ standard to describe what % does; also it's the third word that appears in the description in the Arduino documentation).
Second, the reference should include some examples of what happens when you % negative numbers. Here's where the conceptual difference between "remainder" and "modulo" lies: the result of the former has the same sign as the FIRST operand, whereas the latter would have the one of the SECOND. This is annoying since almost in 100% of the cases where % meets negatives you want the second behavior (e.g. (-13) % 10 yielding 7); however C++ surprises you with the first behavior (-3). Therefore it is important to clarify this in the documentation.

[TheAustrian]

I agree - especially since in the example it's promoted as a way to stay within the bounds of an array. Woe to those who try to count down instead of up in such an instance.

[per1234]

Resolved by: arduino/reference-en#350