Explain the password_confirmation attribute
Merge pull request #34
Typo fixed

An "a" was removed
Typo fixed

"to provide" removed because was duplicated
orthographic and grammatical corrections

- Many orthographic corrections.
    - Added some commas and dots.

- Gramatical corrections:
    - Prevented most self-repetitions.
    - Edited some parts to make a bit clearer.
    - Added ", etc." add the end of lists.
Merge pull request #35 from nicopaez
Merge pull request #37 from 'renich-master'

Conflicts:
	01-00-introduction.md
	01-01-motivation.md