Polish up examples (somewhat)

- Mention them in the docs (arguably a bit hamfistedly).
- Make the README an RST.
- Make them pass flake8 and add flake8 to tox.ini

They should all be rewritten and made Python 3-friendly but that's out
of scope here.
diff --git a/examples/simple/client.py b/examples/simple/client.py
index dff2d03..5662122 100644
--- a/examples/simple/client.py
+++ b/examples/simple/client.py
@@ -8,8 +8,12 @@
 Simple SSL client, using blocking I/O
 """
 
+import os
+import socket
+import sys
+
 from OpenSSL import SSL, crypto
-import sys, os, select, socket
+
 
 def verify_cb(conn, cert, errnum, depth, ok):
     certsubject = crypto.X509Name(cert.get_subject())
@@ -17,20 +21,23 @@
     print('Got certificate: ' + commonname)
     return ok
 
+
 if len(sys.argv) < 3:
     print('Usage: python client.py HOST PORT')
     sys.exit(1)
 
+
 dir = os.path.dirname(sys.argv[0])
 if dir == '':
     dir = os.curdir
 
+
 # Initialize context
 ctx = SSL.Context(SSL.SSLv23_METHOD)
 ctx.set_options(SSL.OP_NO_SSLv2)
 ctx.set_options(SSL.OP_NO_SSLv3)
-ctx.set_verify(SSL.VERIFY_PEER, verify_cb) # Demand a certificate
-ctx.use_privatekey_file (os.path.join(dir, 'client.pkey'))
+ctx.set_verify(SSL.VERIFY_PEER, verify_cb)  # Demand a certificate
+ctx.use_privatekey_file(os.path.join(dir, 'client.pkey'))
 ctx.use_certificate_file(os.path.join(dir, 'client.cert'))
 ctx.load_verify_locations(os.path.join(dir, 'CA.cert'))
 
diff --git a/examples/simple/server.py b/examples/simple/server.py
index bc001ed..19f6d21 100644
--- a/examples/simple/server.py
+++ b/examples/simple/server.py
@@ -8,16 +8,23 @@
 Simple echo server, using nonblocking I/O
 """
 
+from __future__ import print_function
+
+import os
+import select
+import socket
+import sys
+
 from OpenSSL import SSL, crypto
-import sys, os, select, socket
 
 
 def verify_cb(conn, cert, errnum, depth, ok):
     certsubject = crypto.X509Name(cert.get_subject())
     commonname = certsubject.commonName
-    print(('Got certificate: ' + commonname))
+    print('Got certificate: ' + commonname)
     return ok
 
+
 if len(sys.argv) < 2:
     print('Usage: python server.py PORT')
     sys.exit(1)
@@ -30,20 +37,23 @@
 ctx = SSL.Context(SSL.SSLv23_METHOD)
 ctx.set_options(SSL.OP_NO_SSLv2)
 ctx.set_options(SSL.OP_NO_SSLv3)
-ctx.set_verify(SSL.VERIFY_PEER|SSL.VERIFY_FAIL_IF_NO_PEER_CERT, verify_cb) # Demand a certificate
-ctx.use_privatekey_file (os.path.join(dir, 'server.pkey'))
+ctx.set_verify(
+    SSL.VERIFY_PEER | SSL.VERIFY_FAIL_IF_NO_PEER_CERT, verify_cb
+)  # Demand a certificate
+ctx.use_privatekey_file(os.path.join(dir, 'server.pkey'))
 ctx.use_certificate_file(os.path.join(dir, 'server.cert'))
 ctx.load_verify_locations(os.path.join(dir, 'CA.cert'))
 
 # Set up server
 server = SSL.Connection(ctx, socket.socket(socket.AF_INET, socket.SOCK_STREAM))
 server.bind(('', int(sys.argv[1])))
-server.listen(3) 
+server.listen(3)
 server.setblocking(0)
 
 clients = {}
 writers = {}
 
+
 def dropClient(cli, errors=None):
     if errors:
         print('Client %s left unexpectedly:' % (clients[cli],))
@@ -59,20 +69,24 @@
 
 while 1:
     try:
-        r, w, _ = select.select([server] + list(clients.keys()), list(writers.keys()), [])
+        r, w, _ = select.select(
+            [server] + list(clients.keys()), list(writers.keys()), []
+        )
     except:
         break
 
     for cli in r:
         if cli == server:
-            cli,addr = server.accept()
+            cli, addr = server.accept()
             print('Connection from %s' % (addr,))
             clients[cli] = addr
 
         else:
             try:
                 ret = cli.recv(1024).decode('utf-8')
-            except (SSL.WantReadError, SSL.WantWriteError, SSL.WantX509LookupError):
+            except (SSL.WantReadError,
+                    SSL.WantWriteError,
+                    SSL.WantX509LookupError):
                 pass
             except SSL.ZeroReturnError:
                 dropClient(cli)
@@ -86,7 +100,9 @@
     for cli in w:
         try:
             ret = cli.send(writers[cli])
-        except (SSL.WantReadError, SSL.WantWriteError, SSL.WantX509LookupError):
+        except (SSL.WantReadError,
+                SSL.WantWriteError,
+                SSL.WantX509LookupError):
             pass
         except SSL.ZeroReturnError:
             dropClient(cli)