rbperf v0.2.0

Changes

• Added a xtask task to generate the Ruby configuration files which contain details of its ABI we need to walk the stack rather than having all values manually generated. There's still some work to do to avoid duplication and ensure that every value is programmatically generated ec4724d;
• Simplify the Ruby stack walker, which used to be done in two phases. This reduces the number of CPU instructions needed to walk the stack and increases the readability of the code 6f4f78c;