Move repeated import: bats-assert and bats-support to helper file

[MichaelDimmitt]

Hoping the change is helpful. 🙂

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.
• [x] I have added the necessary testing to prove my fix is effective/my feature works (or I did not modify functionality).
• [x] I have added necessary documentation about the functionality in an appropriate .md file.
• [x] I have appropriately commented any code I have modified

Short description of what this PR does:

• Loads bats-support and bats-assert in helper file.
• Easier for future development but less explicit and the same overhead.

Thanks, this project helped me set up bats-assert for my project 💯.

[pimterry]

Nice little improvement. Good spot, thanks!