Fixed the build in order to integrate latest changes available on facebo...

[balena]

...ok/rocksdb repository

[stephan-hof]

Hi

I did a fix

• https://github.com/stephan-hof/pyrocksdb/commit/0c13b55e55ad13056854fef5477f6de797c8f376
• https://github.com/stephan-hof/pyrocksdb/commit/b9f06fe785e10f8cff7fa2c8f99b7bf4a18cd281

Your update of the readme is nice, but I would like to have all the documentation in the .rst files. So they are also visible on readthedocs. If you would like to have ubuntu install instraction, please send a pull request for this file: docs/installation.rst