[BugFix] Pre-Release Bug Fixes

[deeleeramone]

1. Why?:

   • Finding a couple of things going through the testing suite.

2. What?:

   • openbb_imf root folder needs an empty __init__.py file. Pytest didn't know what to do, and it's odd how it didn't happen originally.

   • Unexpected behavior in Tiingo crypto/currency historical price where the interval mapping was not being relayed to the URL.

   • Inconsistent symbol formatting in the returned field from Tiingo/currency. Make uppercase.

3. Impact:

   • Fixes bugs.
   • Improves consistency.

4. Testing Done:

   • Running all the tests.