Adding an `nvm --version` command
Fix NVM_DIR discovery
When curl is not present, immediately bail out of `nvm install` with a nonzero exit code. Fixes #385.
Merge pull request #374 from koenpunt/fix-tests

 Fix NVM_DIR discovery
Merge pull request #382 from koenpunt/version-normalizing

Fix nvm ls for v* numbers
Add Makefile for multishell testing
updated nvm current test for zsh
install shells before running tests
Merge pull request #386 from koenpunt/multi-shell-test

Add Makefile for multishell testing
Adding a trailing newline
Add travis badge to README
Merge pull request #387 from koenpunt/patch-1

Add travis badge to README
added nvm unload method to remove nvm from shell
Added test for nvm unload