Merge branch 'update-cryptography'

CHANGELOG.md

@@ -32,6 +32,7 @@ at anytime.
   * attempt blob downloads from http mirror sources (by default) concurrently to p2p sources
   * replace miniupnpc with [txupnp](https://github.com/lbryio/txupnp). Since txupnp is still under development, it will internally fall back to miniupnpc.
   * simplified test_misc.py in the functional tests
+  * update `cryptography` requirement to 2.3
 
 ### Added
   * `skipped_components` list to the response from `status`

requirements.txt

@@ -1,6 +1,6 @@
 certifi==2018.4.16
 Twisted==16.6.0
-cryptography==2.2.2
+cryptography==2.3
 appdirs==1.4.3
 argparse==1.2.1
 docopt==0.6.2