make importing of drawing and geo subpackages optional

diff -Naur networkx-1.8.1.orig/networkx/__init__.py networkx-1.8.1/networkx/__init__.py
--- networkx-1.8.1.orig/networkx/__init__.py	2013-08-04 13:53:31.000000000 +0000
+++ networkx-1.8.1/networkx/__init__.py	2014-03-14 17:21:05.240698548 +0000
@@ -79,6 +79,8 @@
 from networkx.linalg import *
 from networkx.tests.test import run as test
 
-import networkx.drawing
-from networkx.drawing import *
-
+try:
+    import networkx.drawing
+    from networkx.drawing import *
+except ImportError:
+    pass
diff -Naur networkx-1.8.1.orig/networkx/readwrite/__init__.py networkx-1.8.1/networkx/readwrite/__init__.py
--- networkx-1.8.1.orig/networkx/readwrite/__init__.py	2013-08-04 13:53:31.000000000 +0000
+++ networkx-1.8.1/networkx/readwrite/__init__.py	2014-03-15 23:58:54.524347105 +0000
@@ -13,4 +13,8 @@
 from networkx.readwrite.gml import *
 from networkx.readwrite.graphml import *
 from networkx.readwrite.gexf import *
-from networkx.readwrite.nx_shp import *
+
+try:
+    from networkx.readwrite.nx_shp import *
+except ImportError:
+    pass