Jump to root require if not found.
With this it shouldn't matter in which order multiple bundles are added
to the dom. If local require fails to find the module from its map it
jumps the to current root require in the global scope and works its way
back down from there.

Should fix https://github.com/substack/node-browserify/issues/341
parent req no longer needed
camels
0.6.0
add 0.10 tests to travis