Added the LON variant identity_url

For UK Rackspace accounts the identity_url has lon prepended to it
Merge pull request #501 from binocarlos/develop

Added the LON variant identity_url
updated README.rst to include links to the related docs and IRC.
updated README.rst to remove some verbose wording in the Documentation section that did not apply to salt-cloud
Merge pull request #502 from gravyboat/develop

Updates to README.rst.
Add the bootstrap script to `.gitignore`
Enforce the new providers configuration. Refs #239.

* Updated the `old_to_new()` function to produce a more salt like syntax.
* Added a cli option argument to allow providing a different file which would contain the several cloud providers configuration.
* Besides the separate file for the could providers configuration, we also added support to include any `*.conf` file from `cloud.providers.d/` which is relative to the parent directory of the provided cloud providers configuration file.
* Update the several documentation files in order to include examples of both the old and new cloud providers configuration syntax side-to-side.
Add `get_config_value()` which searches and returns a setting in a known order.

1. In the virtual machines configuration
2. In the virtual machine's provider configuration
3. In the salt cloud configuration
4. Return the provided default
Added a helper function `is_provider_configured()` to `saltcloud.config`.

This function checks all defined provider configurations of the X cloud provider to see if any of them is fully configured.
Migrated the `EC2` cloud driver to use `saltcloud.config.get_config_value()`
`provider` is also a required key using the new configuration format.
Update the EC2 driver docstring to include new configuration syntax.
Fix filename example.
Updated GoGrid driver to use the new syntax and helper functions.
Lower line length by aliasing `saltcloud.config` to `config`.
Some cloud provider configs might not yet include the provider setting.
Add a docstring and fix some arguments passed.
Some more helpful logging.
Default values should not be empty strings.
Fix loading providers data from the new file locations and the search for at least one specific provider configuration.