Remove getTips api command

[lzpap]

Description of change

fixes #318
getTips api endpoint is deprecated in IRI 1.8.6.

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How the change has been tested

Unit tests pass.

Change checklist

• My code follows the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (docs/ directory and/or docstrings in source code)
• I have followed PEP-8 Style Guide in my code.
• New and existing unit tests pass locally with my changes

[todofixthis]

LGTM