fixed NVM installation issue

[bongani-m]

While install on a fresh Mojave installation I ran into two issues: 1) NVM was getting skipped and 2) installation did work because ~/.bash_profile did not exist.

This fix resolves both issues by checking for existance of NVM_DIR to see if nvm is installed and creating the ~/.bash_profile if it doesn't already exist. It also loads nvm for the session to insure that node and the npm packages get installed gets installed. Also NVM gets a version bump

Fixes #7

[alexfrommars]

It still is skipping the NVM install