feat: Service Tests are robust now. Manual login not required to run test suite.

[yugantarjain]

Description

This PR implements temp keychain allocation and deallocation in test classes so that the test suite can be run easily and not require manual login beforehand.

This PR also updates the Travis and it now runs the Xcode test suite.

Fixes #119

Type of Change:

• Code
• Quality Assurance
• Documentation

Code/Quality Assurance Only

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Tested on Xcode.

Checklist:

• [x] My PR follows the style guidelines of this project
• [x] I have performed a self-review of my own code or materials
• [x] I have commented my code or provided relevant documentation, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] Any dependent changes have been merged

Code/Quality Assurance Only

• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been published in downstream modules

[yugantarjain]

@anitab-org/mentorship-ios-maintainers merge conflicts resolved.