Catch base S3 exception and show a nice error msg
Improve documentation of the interactive client

All the commands now inherit from this custom class `BaseCmd`
that basically provides a detailed `usage` method. The sync
command received special care cause of its differences from
the other commands.
Reading required config vars from the environment

Now, instead of creating a config file, the user is also able to feed
the ranger's config needs with environment variables. Just export the
variables that you would put in the file and we're good to go.
Updating the example config file
Moving old docs to a sub folder
Small improvement for the main description
Adding copyright notice to all the files
Removing unused code
Adding the `--delimiter` option to the `list` command

Now, the user can decide which caracter will be used to separate columns
when printing out items found on s3 buckets.
Fixing and improving the params of the Url command

Now the `url` command also takes the `--public` parameter to generate a
public, but not authenticated, url for the object;

This new option is mutually exclusive with the `--method` parameter.

Bugs fixed:

 * The parameter `--method` was wrongly set up, so it was not actually
   reading the value from the command line.
New release: 0.3.0