Please note that there are some works planned on certain lines that will close them for parts of the summer.
EDIT:: This closure is over now (8/24/2015) !From July 25 through August 23rd, the RERA will be closed between Auber and La Défense.
EDIT : This closure is over now (8/24/2015) ! From July 15 through August 22, the RERC will be closed between Gare d'Austerlitz, Avenue Henri-Martin, and Javel.
Also of note, from August 3-30, the metro station Basilique de Saint-Denis on line 13 will be closed.
For a map summarizing the closures, please see this link (in French):
http://www.leparisien.fr/paris-75/metro-rer-transilien-attention-aux-travaux-02-07-2015-4913543.php
A few vocab notes to help you with the map:
Fermeture means closed
Trafic Interrompu means *Traffic Interrupted * (i.e. closed!)
You can see from the map that I only reported a few of the closures in the text of my message. There are others.