Update version to 2.1

Doxyfile

@@ -38,7 +38,7 @@ PROJECT_NAME           = GalSim
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 2.0
+PROJECT_NUMBER         = 2.1
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a

README.md

@@ -47,10 +47,10 @@ You can also use conda via conda-forge
 Source Distribution
 -------------------
 
-The current released version of GalSim is version 2.0.  To get the code, you
+The current released version of GalSim is version 2.1.  To get the code, you
 can grab the tarball (or zip file) from
 
-    https://github.com/GalSim-developers/GalSim/releases/tag/v2.0.0
+    https://github.com/GalSim-developers/GalSim/releases/tag/v2.1.0
 
 Also, feel free to fork the repository:
 
@@ -214,7 +214,7 @@ at one time or another.
 The version of the code at any given snapshot can be downloaded from our
 GitHub webpage, or checked out from the repository using the tag name, e.g.:
 
-    git checkout v2.0.0
+    git checkout v2.1.0
 
 This will then update your directory tree to the snapshot of the code at the
 milestone requested.  (You will also get a message about being in a "detached"