Libify byebug executable!

We are finally able to test byebug started as a script.
Add bindir to gemspec
Double check TracePoint API info

We don't want to segfault because of corrupted info.
Fix some indentations
Print debug info after the stacksize is updated
Fix problems in the test suite with interpolation
Indent "when" like "case"
Remove unnecessary line in test_helper
Remove duplicated file
Done!