Clean up intro activity and layout

[qqdasdzxc]

Hello, my name is Dmitry
I am very impressed with the project and it would be great to help with the development with contributions

I am an android developer with almost 5 years of experience in production
CV is attached
Kuzmin Dmitriy.pdf

What was done in this pull request:

1. Removed unused code from IntroActivity
2. Simplified layout of activity_intro
3. Removed the dependency of the shimmering library
4. Create helper method for wrapping a string into a color in html format (later you can be applied on other screens)

Do you need this kind of contribution? Maybe there is a list of urgent tasks that I can help with?

[soaryong-c]

@qqdasdzxc
Thank you very much for your contribution.
Right now we're refactoring the whole thing, so it's hard to apply.
I will refer to the code you wrote when refactoring.

[qqdasdzxc]

soaryong-c
I understand the pain of a big refactoring :D
So it would be cool to know when and how I can help by contributions, I have a great desire to help this project by development
Thank you!