mv fails on block, character, fifo

[aeosynth]

from #23:

a block device (mknod test/resources/block b 1 1) causes the following error:

Running test: mv.js
shell.js: internal error
Error: UNKNOWN, unknown error
    at Object.fs.readSync (fs.js:381:19)
    at copyFileSync (/Users/james/src/assets/shelljs/shell.js:1119:20)
    at /Users/james/src/assets/shelljs/shell.js:311:5
    at Array.forEach (native)
    at Object._cp (/Users/james/src/assets/shelljs/shell.js:270:11)
    at Object.cp (/Users/james/src/assets/shelljs/shell.js:1074:23)
    at Object.<anonymous> (/Users/james/src/assets/shelljs/test/mv.js:20:7)
    at Module._compile (module.js:449:26)
    at Object.Module._extensions..js (module.js:467:10)
    at Module.load (module.js:356:32)

a character device (mknod test/resources/character c 1 1) and fifo (mkfifo test/resources/fifo) causes the mv test to hang

symlink, file, directory work fine. haven't tested sockets.