Fix initial move of servo motor

[sapics]

This PR would fix the problem which is reported in #14 .
I guess that it makes same initial move as Servo library
and this could also avoid initial movement with .attach(...,0)
which would be new feature.
And it would also close #25 #26 .

This PR changes the initial state of servo.ticks and
I have not tested this PR yet, because I don't have servo motor, sorry.
Thus, it might be better to apply this PR after someone's test report.
I create this PR with reference to https://stackoverflow.com/questions/40892922/.

And I am not good at English, thus, if you know better English words,
please fix variable name and comments.

[sapics]

This PR add the new method .attach(pin, min, max, initialPulseWidth).
If we could not add new method for compatiblity with Servo library, I will create a new PR which is compatible with Servo library.
But it moves to DEFAULT_PULSE_WIDTH with .attach.

[Dakkaron]

I know the repo is officially unmaintained, but would it still be possible to merge this?