Make main(), drop pylint directives and some funcs

Make a `main` function at the very top of the `katello_rapidnode` module. Push
logic from the bottom of the module in to this function. Place this at the
bottom of the module instead:

    if __name__ == '__main__':
        main()

It should now be possible to import the `katello_rapidnode` module without
triggering side effets like, uh... setting up a capsule. This should make it
possible to create unit tests.

Drop several `pylint:disable` directives:

1. W0621 (redefining-name-from-outer-scope)
2. W0632 (possible-unbalanced-tuple-unpacking-with-sequence)

The first issue is fixed by moving logic in to function `main`. The `child`
variable no longer conflicts with the `child` argument to several functions. The
second issue was fixed by f4cbc54ae61d77837ce6e73455bba1f47898c75a.

Drop the `get_parent` and `get_children` functions. They are extremely
simplistic single-use functions.
Merge pull request #8 from Ichimonji10/dont-ignore-crap

Make main(), drop pylint directives and some funcs
Drop read_config_file, refactor child_register

Drop function `read_config_file`. It does nothing more than return a tuple of
values from the config file. The contents of the config file are available to
all functions via the global variable `CONFIG`, so this extra level of
indirection is not necessary.

Refactor function `child_register`. It made the most extensive use of
`read_config_file` via this line of code:

    adminpassword, orgname, contentview = read_config_file()[4:7]

It was also a bit messy in general.

Both the Python 2 and 3 versions of flake8 and pylint are happy with the script.
Merge pull request #10 from Ichimonji10/drop-func

Drop read_config_file, refactor child_register
Add unit tests for function `parent_get_capsules`

Also clean up function `parent_get_capsules`. The new unit tests are basic, but
they do prove that it is possible to import module `katello_rapidnode` without
negative side effects and create unit tests for the code therein.