Updated content to fit original repo

[timnqp]

1. Updated table of content
2. Swapped Classes & SOLID
3. Updated example functions in Objects and Data Structures

[hienvd]

@quangphuc789
The anchor link to 6.SOLID in table of content seems doesn't work when I click on it.
Please take a look.

[timnqp]

@hienvd @tiennv91 I have made the changes to add anchor link to 6. SOLID
I have made another pull request. Can you review?

#15

[hienvd]

It works now, thanks @quangphuc789
Btw, no need to create another PR.

@tiennv91: Looks good to me, waiting for your review :)

[timnqp]

@hienvd @tiennv91 I have made a new commit, which updated the Chinese language versions. Cheers :)