Made optional dependencies as list in readme

README.rst

@@ -193,7 +193,7 @@ Optional dependencies
 ^^^^^^^^^^^^^^^^^^^^^
 The following dependencies are not automatically installed upon installation of ``VIP`` but may significantly improve your experience:
 
-- ``VIP`` contains a class ``vip_hci.fits.ds9`` that enables, through ``pyds9``, the interaction with a DS9 window (displaying numpy arrays, controlling the display options, etc). ``pyds9`` is an optional requirement and must be installed from the latest development version: ``pip install git+git://github.com/ericmandel/pyds9.git#egg=pyds9``
+- ``VIP`` contains a class ``vip_hci.vip_ds9`` that enables, through ``pyds9``, the interaction with a DS9 window (displaying numpy arrays, controlling the display options, etc). To enable this feature, ``pyds9`` must be installed from the latest development version: ``pip install git+git://github.com/ericmandel/pyds9.git#egg=pyds9``
 - Also, you can install the Intel Math Kernel Library (``mkl``) optimizations (provided that you have a recent version of ``conda``) or ``openblas`` libraries. Either of them can be installed with ``conda install``. This is recommended along with ``OpenCV`` for maximum speed on ``VIP`` computations.
 - ``VIP`` offers the possibility of computing SVDs on GPU by using ``CuPy`` (starting from version 0.8.0) or ``PyTorch`` (from version 0.9.2). These remain as optional requirements, to be installed by the user, as well as a proper CUDA environment (and a decent GPU card).
 - Finally, bad pixel correction routines can be optimised with ``Numba``, which  converts some Python code, particularly ``NumPy``, into fast machine code. A factor up to ~50x times speed improvement can be obtained on large images compared to NumPy. Numba can be installed with ``conda install numba``.