feat(indra): fetch networks from indra cogex and visualize with cytoscape

[tonywu1999]

Motivation and Context

We want to integrate the statistical results of MSstats with prior literature extracted from INDRA. See this description for further information on INDRA.

Changes

• Create 2 new functions to handle integration with INDRA. The first function fetches data from INDRA, filters and processes the response (e.g. collapsing duplicate edges), and provides dataframes of relationships. The second function visualizes it on Cytoscape.
• Added testing framework with testthat. I believe we should start using testthat long term since it provides many additional functionalities compared to tinytest, such as mocking the output of functions. We don't have many unit tests in MSstats anyways (I think some of them aren't actually being executed), so I can migrate unit tests to testthat in the future.

Testing

• Added a unit test verifying that the correct number of nodes and edges are returned given a mock response from INDRA and a mock dataset from the MSstats group comparison function.

Checklist Before Requesting a Review

• I have read the MSstats contributing guidelines
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

[tonywu1999]

Closing this PR in favor of Vitek-Lab/MSstatsBioNet#1