exit 1 on failure to create NOTES_DIRECTORY

[rmNULL]

Fixes

Fixes #55 Closes #55

Checklist

• [x] I have made a change to this repository, be it functionality, testing, documentation, spelling, or grammar.
• [x] I updated my branch with the master branch.
• [ ] I have added the necessary testing to prove my fix is effective or my feature work, or I did not modify functionality.
• [ ] I have added necessary documentation about the functionality in an appropriate .md file
• [x] I have commented any code I have modified or I did not modify any code

Short description of what this PR does:

• When mkdir fails create NOTES_DIRECTORY, it exits with an error message to user

[primis]

It looks great, but I might suggest adding a "please" to the change to sound nicer. Or an explanation like "Could not create the notes directory, please change..." for verbosity sake.

[rmNULL]

okay, sure.

[pimterry]

I've added a couple of bonus tweaks to this (and tests), but overall it looks great to me! Merging now.

[rmNULL]

Lol nice. "Could not create directory " will be redundant output as mkdir outputs a similar message. Maybe we should redirect mkdir to /dev/null