build: support node.js >= 0.8

This module doesn't do anything special, so it should support node.js 0.8 "officially" by building on it in Travis CI. `cogent`, at least, uses the newer caret-style for a dependency, so doesn't want to install on node.js 08. on Travis CI :(

If cogent doesn't want to change, since this is just required for the build.js script and not to test, I made Travis CI ignore the co* devDependencies so it can test on node.js 0.8?

What do you guys think about including this commit? I would love to be able to not support node.js 0.8...