version bump 0.3.12: workaround for node bug

- refuse to run `j` on node v0.10.31 (h/t @lightbringer1991, fixes #4)
- use concat-stream and check process.stdin.isTTY (h/t @sindresorhus)
- CI pinned to node 0.10.31 (see https://github.com/joyent/node/issues/8208)
- updated XLS to 0.7.1, XLS to 0.7.9
- added --sheet-index option to specify by index rather than by name