Now that we load this file before loading the `_settings.scss` file, we
can safely use the `!default` flag.
This makes it easier to override these variables by adding a new file
and loading it before `_consul_settings.scss` is loaded. For instance,
we've got this code related to the `$brand` variable:
```
$brand: #004a83 !default;
$brand-secondary: darken($brand, 10%) !default;
$dark: $brand-secondary !default;
$link: $brand !default;
$debates: $brand !default;
$tooltip-background-color: $brand !default;
```
If we override `$brand` in `_custom_settings.scss`, variables like
`$link` won't be affected by this change. In order to do so, we'd need
to load `_custom_settings.scss` before loading `_consul_settings.scss`.
So why aren't we loading `_custom_settings.scss` first, just like we
load `_consul_settings.scss` before loading `_settings.scss`? Mainly,
compatibility reasons. Some people might have this code in their
`_custom_settings.scss` file:
```
$dark: darken($brand, 30%);
```
If we load this file before loading `_consul_settings.scss`, we'll get
an error because `$brand` isn't defined at this point.
So we're introducing a new file where variables can be overriden before
they are defined while keeping the option to override them after they
are defined.
We're updating the comments in these files to define the new behavior,
and removing the links (which point to places which don't exist since
commit 392d633d2) in order to make it easier to read the comments.
