Refactor opcodes conditionals

This refactor is probably slower, but I think is less verbose
and easier to check/debug. Also, there is room for optimizations later
using a decision tree instead of regexs.
Merge branch 'master' into topic-refactor-opcode-conditionals
Merge pull request #3 from hugoArregui/topic-refactor-opcode-conditionals

Topic refactor opcode conditionals