Customize slider height and track colors

[bcarreon]

Before you make a Pull Request, read the important guidelines:

Issue Link 🔗

• Is this a bug fix or a feature?
• Does it break any existing functionality?

Goals of this PR 🎉

• Why is the change important?
• What does this fix?
• How far has it been tested?

How Has This Been Tested 🔍

Please let us know if you have tested your PR and if we need to reproduce the issues. Also, please let us know if we need any relevant information for running the tests.

• User Interface Testing
• Application Testing

Test Configuration 👾

• Xcode version:
• Device/Simulator
• iOS version || MacOSX version

Things to check on 🎯

• My Pull Request code follows the coding standards and styles of the project
• I have worked on unit tests and reviewed my code to the best of my ability
• I have used comments to make other coders understand my code better
• My changes are good to go without any warnings
• I have added unit tests both for the happy and sad path
• All of my unit tests pass successfully before pushing the PR
• I have made sure all dependent downstream changes impacted by my PR are working

[croossin]

LGTM 👍