fixes

README.md

@@ -68,12 +68,13 @@ Plotting support is added via:
 
     pip3 install --user matplotlib
 
-FFTW support is added via:
+NIFTy uses Numpy's FFT implementation by default. For large problems FFTW may be
+used because of its higher performance. It can be installed via::
 
     sudo apt-get install libfftw3-dev
     pip3 install --user pyfftw
 
-To actually use FFTW in your Nifty calculations, you need to call
+To enable FFTW usage in NIFTy, call::
 
     nifty5.fft.enable_fftw()
 
@@ -97,7 +98,7 @@ MPI support is added via:
 
 To run the tests, additional packages are required:
 
-    sudo apt-get install python3-coverage python3-pytest python3-pytest-cov
+    sudo apt-get install python3-pytest-cov
 
 Afterwards the tests (including a coverage report) can be run using the
 following command in the repository root: