Switch from /bin/sh to /bin/bash

You have bashisms in your script and /bin/sh might not always be bash. In that case the script would fail (for example on Ubuntu).
Remove unneeded shebang in nvm.sh
Added command to get current nvm environment.
Added test for `nvm current`
Universal test of unsetopt command

According to http://stackoverflow.com/a/7522866/189431 it should work in "bash, zsh, ksh and sh (as provided by dash)".
Merge pull request #322 from koenpunt/fix-unsetopt-test

Universal test of unsetopt command. Closes #300
Slurp test unsetopt stderr
Merge pull request #324 from hurrymaplelad/quiet_type

Slurp stderr from  test unsetopt
helper method for testing existence of commands
Merge pull request #326 from koenpunt/has-command-helper

helper method for testing existence of commands
fix copy-packages
fix copy-packages in zsh (without breaking sh and bash)
Merge pull request #327 from stuartf/issue-314

fix copy-packages
merge in changes from creationix/nvm
Merge pull request #328 from naartjie/master

fix copy-packages in zsh (without breaking sh and bash). Closes #223, fixes #299.
Update nvm.sh

small fix fo nvm help info
Update nvm.sh

Fix - this line should be nvm use 0.10 - no 'v', and no incremental version number.
Update README.markdown
Merge branch 'master' into add-current-command
Merge pull request #331 from deiga/patch-1

Update README.markdown