fix tests
Merge pull request #221 from alex/tim/String#getbyte

add String#getbyte
Merge pull request #222 from alex/tim/String#index

Add String#index
move classes to top-level, subclass object
eliminate dead code that came over from Rubinius
remove Environment class and use Glob class to keep state
simplify separator access
differentiate naming for glob and glob pattern
make it more clear that third argument is ignored here
exception handler only around exceptional method
raise OSErrors from low-level dir functions
use Dir.chdir with block, so we revert back to the original working dir in tests
forgotten import
simpler rmdir
make closing work correctly and add test
nits
I always confuse next and continue
nudge travis
re-add method lost in refactoring
hate doing this, but don't want to have to expose DIR struct fields just so we can ha have it as a nullptr, and OpaquePtrs don't work for nullptr