Silence stderr warning on `nvm uninstall' with no configured alias
Reduce usage of `cd' to avoid issues with shell aliases

Since we run in interactive context the builtin `cd' may have been aliased to
print some additional info when invoked, thus it's safer for us to avoid
parsing the output from subshells which calls it.

For instance in .bash_profile I have the following function to redefine
`cd' such that it will list the destination directory contents:
cd () { builtin cd "$@" && ls -F --color=auto }
Merge pull request #203 from em-/master

Don't trust the environment and explicitly ask for the builtin `cd'