Citus_indent setup

The steps described in our README does not work for me: https://github.com/citusdata/citus/blob/master/CONTRIBUTING.md#following-our-coding-conventions

The main problem is that after cloning the `tools` repo we need to run `make install` from top level instead of `uncrustify` because many of the variables are defined at the top level.

Start with the coding-conventions section in CONTRIBUTING.md and follow its setup steps against the tools repository. Verify the documented command matches the required top-level `make install` flow, and confirm the instructions work for setting up Citus_indent.

Written by the indexing model from the issue text.