Add size option, update readme

[artemkosenko]

Hello there.

I propose two things:

1. An additional boolean configuration parameter 'adjustOverlaps'.
   The reason for that is that I have more 'out-connections' than 'in-connections'. (basically elements may fall into multiple categories)
   
   It doesn't look nice.
   So the 'adjustOverlaps === true' param does the following:
   

By default it is set to 'false'. The usual logic stays the same.

2. An updated way to calculate the largest node.
   This is a controversian one. But it helped me.
   The problem was due to the described above thing - more 'out-connections' than 'in-connections'.
   The 'findLargestNode' returned a node from a middle which then led to a visual bug.
   It got:
   
   But i expected one of the images above.

I added the 'tree.html' file which can reproduce the issue if the 'findLargestNode' function is reverted back.
Also there is a test for that.
expect(oneThenTwo).toEqual(jasmine.objectContaining({y: 28}));
It failed here because 'y' was undefined;

The controvercial thing is that a few tests are broken because charts do not conform to the png images provided.
I'd be nice you if could help with those images.

Thanks

[artemkosenko]

I realized that I needed to use node priorities to get what i wanted.
So I reverted back the second change.

[kurkle]

I don't like the adjustOverlap as a option name.

What do you think about size: 'min' (default 'max')? Should work both ways and can be determined like Math[options.size](node.in, node.out)

That would determine the node height. The flows would then be aligned using a simple multiplier (in/height or out/height), which can always be used, and should be limited to be <=1.

[sonarqubecloud]

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[kurkle]

I'll need to do some testing before releasing this, but I'll be away for couple of weeks. So be patient.

[artemkosenko]

Sure. Take you time.

[sonarqubecloud]

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