update doc

Author: rflamary

docs/source/readme.rst

@@ -47,7 +47,7 @@ it) on you machine using
 
 ::
 
-    python setup.py install --user
+    python setup.py install --user # for user install (no root)
 
 The toolbox is also available on PyPI with a possibly slightly older
 version. You can install it with:
@@ -65,6 +65,28 @@ without errors:
 
 Note that for easier access the module is name ot instead of pot.
 
+Dependencies
+~~~~~~~~~~~~
+
+Some sub-modules require additional dependences which are discussed
+below
+
+-  ot.dr (Wasserstein dimensionality rediuction) depends on autograd and
+   pymanopt that can be installed with:
+
+   ::
+
+       pip install pymanopt autograd
+
+-  ot.gpu (GPU accelerated OT) depends on cudamat that have to be
+   installed with:
+
+   ::
+
+       git clone https://github.com/cudamat/cudamat.git
+       cd cudamat
+       python setup.py install --user # for user install (no root)
+
 Examples
 --------
 
@@ -103,6 +125,8 @@ The contributors to this library are:
 -  `Nicolas Courty <http://people.irisa.fr/Nicolas.Courty/>`__
 -  `Laetitia Chapel <http://people.irisa.fr/Laetitia.Chapel/>`__
 -  `Michael Perrot <http://perso.univ-st-etienne.fr/pem82055/>`__
+   (Mapping estimation)
+-  `Léo Gautheron <https://github.com/aje>`__ (GPU implementation)
 
 This toolbox benefit a lot from open source research and we would like
 to thank the following persons for providing some code (in various