Simplify pixel comparison and improve performance

[mourner]

• Refactor the code to inline and simplify as many calculations inside colorDelta as possible, paving the way for landing Transparent is not white #142 and improving performance by ~6%.
• Add a rudimentary benchmark to make sure we don't regress.
• Fix an issue after Handle “undefined” as passed option values #146 where not passing options would cause an error.
• Upgrade dev dependencies.