Fix typos found by codespell

Signed-off-by: Stefan Weil <sw@weilnetz.de>

bootstrap/_suse_common.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-# SLE12 dont have python-virtualenv
+# SLE12 don't have python-virtualenv
 
 zypper -nq in -l git-core \
   python \

docs/ciphers.rst

@@ -105,7 +105,7 @@ https://wiki.mozilla.org/Security/Server_Side_TLS
 
 and the version implemented by the Let's Encrypt client will be the
 version that was most current as of the release date of each client
-version. Mozilla offers three seperate sets of cryptographic options,
+version. Mozilla offers three separate sets of cryptographic options,
 which trade off security and compatibility differently. These are
 referred to as as the "Modern", "Intermediate", and "Old" configurations
 (in order from most secure to least secure, and least-backwards compatible

letsencrypt/client.py

@@ -430,7 +430,7 @@ class Client(object):
         except:
             # TODO: suggest letshelp-letsencypt here
             reporter.add_message(
-                "An error occured and we failed to restore your config and "
+                "An error occurred and we failed to restore your config and "
                 "restart your server. Please submit a bug report to "
                 "https://github.com/letsencrypt/letsencrypt",
                 reporter.HIGH_PRIORITY)