Simplifies parse_* function's arguments

-makes these functions receive only two arguments: ts and elements
-`parse_args` becomes simpler
Removes warnings when -Wall is used
Removes pep8 warnings on docopt_c.py
Optimizes usage section get+verification

- Respects pep8
- 4 lines of code
Merge pull request #21 from ffunenga/fix-pep8-docopt-c

Fixes pep8 warnings in docopt_c.py
Merge pull request #20 from ffunenga/simplify-parse-functions

Simplify parse functions