Several fixes in the documentation

- The location of the configuration definition (files and env variables)
  is now properly explained.
- All normal sentences begin with capital letters.
- Removed uses of 'indent' as a noun; changed them to 'indentation'.
- Changed references to `i_with ' to `with' in the documentation text.
- Changed the final `never' to `always' for strict_with
- Tiny amounts of rewording to improve grammar, style, and consistency.
- Explain the input and output behaviour in the DESCRIPTION section.
Improve the LICENSE section

- The name of the license is corrected.
- The location of the license in the sources is explicitly mentioned.
- Removed clauses that are redundant with the license.