Documentation clean-up

[pleonex]

The current documentation format needs a clean-up. Thanks for the feedback of @iblancasa in #7, I realized that we are duplicating the documentation in the header of the files and in the class descriptions.

We need to focus mainly in the output that the help() function gives for the packages. For instance:

>> help(custom.custom)
Help on module custom.custom in custom:
NAME
    custom.custom - Log parsing functions for custom logs.
FILE
    /home/benito/Projects/logparser/src/custom/custom.py
DESCRIPTION
    Functions:
      + on_custom_log: Parse a log with a custom prefix.
FUNCTIONS
    on_custom_log(match, state)
        Parse a log with a custom prefix.

These are some of the tasks we need to do:

• Add style guide to the CONTRIBUTING.md file.
• Remove function list in package description.
• Remove method list in class description.
• Review the package and class description and summary.
• Add arguments description in the method and function docs.

[iblancasa]

What do you think about use doctest?
The size of the files will be increased but it will help to read the code and know the expected output of the methods. Also, it will help with #3