Fixed `nvm_version_greater` has syntax error in zsh-buildin-command `[`
Fix tests so that they fail in zsh (for #505)
Merge pull request #505 from magicdrive/fix-error_nvm_version_greater

Fixed `nvm_version_greater` has syntax error in zsh-builtin command `[`
Removing an invalid option to `touch` from this test.
Add error checking to nvm_tree_contains_path