fix for #2 & #3 (also updates SniffTest.php)

[bkdotcom]

refactor MaximumComplexitySniff and Analyzer to utilize "$phpcsFile" and how nestingIncrement is calculated

[Rarst]

Hey, thanks for PR! This looks to touch a lot in tests (I saw you mentioned you had trouble), with some cosmetic changes on top, and tests failed in Scrutinizer after.

Since it's all one commit it would be hard for me to separate out what happens why.

Would you mind making PR with just your code changes and adding a new unit test for them, without changing how unit tests work? It's ok if tests don't work at that point, I will look into what's wrong with them, but that's tangential to code changes.

If not I will try sort it out of this, but will probably take me longer to get to that. :)

[bkdotcom]

@Rarst : I've created #5 without the update to SniffTest

However It's still necessary to modify AnalyzerTest
reason
Analyzer::computeForFunctionFromTokensAndPosition's signature changed to
to public function computeForFunctionFromTokensAndPosition(File $phpcsFile, int $position): int
(previously first param was an array of tokens)

[Rarst]

Replaced by #5