Simplify scripts, format, allow for config-file readout, DRY

@pkorshunov, @amohammadi could you please review this and merge it. This MR includes the following changes:

• Format all help messages to 80 characters (POSIX compliance)
• Include examples in the help messages (moved from the README)
• Add instructions on the README on how to create an environment and how to setup python-gitlab
• Delay the import of gitlab till when it is actually needed, so at least the help message can be printed
• Implement import checks and print an clean error message if one of the packages (gitlab, docopt) is not installed
• Remove duplicates in the documentation/README and leverage the --help message from each script (DRY)
• Allow the scripts to work against ~/.python-gitlab.cfg or /etc/python-gitlab.cfg instead of requiring a token on the command line
• Ask for a token (via input()) if it cannot read the configuration file

added 5 commits

• 4e742770...656e9530 - 4 commits from branch master
• 4300a52d - Simplify scripts, format, allow for config-file readout, DRY

Compare with previous version

@andre.anjos looks generally okay. There are some code duplication which can only be fixed if it was all in a package.

I would drop the dependency on Numpy as well since it's a large dependency.

added 3 commits

• eea0a364 - Drop dependency to numpy; Rename
• 20b740fa - Provide a more sensible default
• 88e519f8 - Change mode default to mrs; Drop py2 support

Compare with previous version

resolved all discussions

Numpy dependence dropped.

There is one thing that bothers me a bit is the repetition: if you're releasing a single package, you need to provide the -p flag on release.py. But your changelog only contains that package anyways, so I don't understand why you need both. Do we?

@amohammadi: please have a look/merge if that works for you.

merged

mentioned in commit 4fe4e5ed