Simplified `Composer\Package\LinkConstraint\MultiConstraint#__toString()`, using `(` and `)` for delimiters
Adding stricter parsing output format test to ensure bijective constraint syntax for composite constraints
Adding test cases to verify bijective nature of parsing and casting to string of multi constraints
Merge pull request #1 from Ocramius/feature/lexer-parsing-multi-constraint-syntax-fixes

Feature/lexer parsing multi constraint syntax fixes