Fix documentation path exports and other little things

[airswing]

Description

Modified the README.md to make exporting paths work after cding into the agave-cli directory. Fixed git command and other small things like formatting in shell blocks and spelling. Fixed a spelling error in auth.rst

https://github.com/TACC-Cloud/agave-cli/issues/94

• [x] I have raised an issue to propose this change (required)

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ ] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [ ] I have signed-off my commits with git commit -s
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.