[mod] upgrade requirements.txt

requirements.txt

-certifi==2016.9.26
+certifi==2017.1.23
 flask==0.12
 flask-babel==0.11.1
-lxml==3.7.1
-ndg-httpsclient==0.4.2
-pyasn1==0.1.9
+lxml==3.7.3
+idna==2.5
 pygments==2.1.3
 pyopenssl==16.2.0
-python-dateutil==2.5.3
-pyyaml==3.11
-requests[socks]==2.12.4
+python-dateutil==2.6.0
+pyyaml==3.12
+requests[socks]==2.13.0

searx/webapp.py

 from searx.preferences import Preferences, ValidationException
 from searx.answerers import answerers
 
-# check if the pyopenssl, ndg-httpsclient, pyasn1 packages are installed.
-# They are needed for SSL connection without trouble, see #298
+# check if the pyopenssl package is installed.
+# It is needed for SSL connection without trouble, see #298
 try:
     import OpenSSL.SSL  # NOQA
-    import ndg.httpsclient  # NOQA
-    import pyasn1  # NOQA
 except ImportError:
-    logger.critical("The pyopenssl, ndg-httpsclient, pyasn1 packages have to be installed.\n"
+    logger.critical("The pyopenssl package has to be installed.\n"
                     "Some HTTPS connections will fail")
 
 # serve pages with HTTP/1.1