Fix a typo in readme

[PDWhittington]

Hi,

First and foremost -- thanks for this tool. I am shortly going to try and build it and it looks like just what I need!

I wanted to correct a typo in readme.md:

You can also build it from source, but this is not recommended if your are only going to use Fluor in the regular way, and not hack it.

should be

You can also build it from source, but this is not recommended if you are only going to use Fluor in the regular way, and not hack it.

I tried to push a branch up and raise a PR but I don't have permissions.