Avoid carrying over test status when no node version is installed

When sourcing nvm.sh, if there are no version of node installed the command
`nvm ls default` silentry fails, however it's return status code (`$?`) is
still set to non-zero, which means an error.

This patch simply avoids this issue by making sure the status code after
sourcing is ok so that people that put the returned status codes in their
command line prompt don't get an error every time `nvm.sh` is sourced.
remove continue from curl arg. nodejs.org doesnt seems to support continue, CDN effect perhaps?
Supress ZSH "no matches found" error

Fixes issue #39

ZSH's default globbing behaviour differs from Bash. If there is no
match, ZSH itself will print the error message.

This means that piping a commantd's STDERR to /dev/null will not
hide it.

By unsetting the NOMATCH option we get a behaviour similar to Bash.

Signed-off-by: Tomas Sedovic <tomas@sedovic.cz>
Merge pull request #120 from tomassedovic/issue-39-fix-zsh-error-msg

Supress ZSH "no matches found" error
Add explicit MIT license to README
added additional options for compiling node
Merge pull request #125 from fatshotty/master

possibility to pass argument to node while compiling
Fix bug introduced by pull # 125
Added check for unsetopt

unsetopt doesn't exist on OSX by default which causes `. nvm.sh` to
fail at that line.
Merge pull request #129 from indianburger/master

Add check for unsetopt issue #128
Fix parse error in Zsh 4.3.17
Hide errors from `which unsetopt`

Errors occurred when it was run in bash.
Merge pull request #131 from rummik/patch-1

Fix parse error in Zsh 4.3.17
Fix warning when unsetopt isn't found
Merge pull request #133 from mimetnet/master

Fix warning when unsetopt isn't found
changed npm url to use https (script has moved)
Merge pull request #144 from logosity/master

fix for npm install failure (corrects: Issue #91)
add /.nvm to NVM_DIR so we dont clutter up home directories
Revert "add /.nvm to NVM_DIR so we dont clutter up home directories"

This reverts commit a107b12d2ab3484f353e7f8f079a54fcf9ee3d8a.
add v to version if user does not specify it to simplify commands