Token documentation inaccurate

[Marston]

It turns out the user can use their .netrc file to pass in the CMR token. There is no clear examples in the Readme and it is hard to find out the examples, which were inaccurate on how to pass the token into the config dictionary.
As it currently stand, the user should use car-token instead of the standard: Authorization as the dictionary key.
Please fix this to use the standard dictionary language for Bearer tokens and provide simple examples of the use of this powerful API.

[jceaser]

The .netrc example is not to be included in the documentation, but the readme does not show how to use tokens requiring users to go to the notebooks to see examples.

Three changes should be done here:

1. add a short token example to the readme, and point to the notebook for further examples
2. update the token code to return a bearer token so that users do not have to do this on their own.
3. move code off of Echo-Token header and to Authorization header.

[jceaser]

https://bugs.earthdata.nasa.gov/browse/CMR-7405