Run tests against pypy3, use travis's pypy/pypy3 (#743)

diff --git a/.travis.yml b/.travis.yml
index 6a5f3f2..b2499b5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -28,7 +28,10 @@
     env: TOXENV=py35
   - python: "3.6"
     env: TOXENV=py36
-  - env: TOXENV=pypy
+  - python: "pypy"
+    env: TOXENV=pypy
+  - python: "pypy3"
+    env: TOXENV=pypy3
 
   # Also run the tests against cryptography master.
   - python: "2.7"
@@ -39,7 +42,10 @@
     env: TOXENV=py35-cryptographyMaster
   - python: "3.6"
     env: TOXENV=py36-cryptographyMaster
-  - env: TOXENV=pypy-cryptographyMaster
+  - python: "pypy"
+    env: TOXENV=pypy-cryptographyMaster
+  - python: "pypy3"
+    env: TOXENV=pypy3-cryptographyMaster
 
   # And current minimum cryptography version.
   - python: "2.7"
@@ -50,7 +56,10 @@
     env: TOXENV=py35-cryptographyMinimum
   - python: "3.6"
     env: TOXENV=py36-cryptographyMinimum
-  - env: TOXENV=pypy-cryptographyMinimum
+  - python: "pypy"
+    env: TOXENV=pypy-cryptographyMinimum
+  - python: "pypy3"
+    env: TOXENV=pypy3-cryptographyMinimum
 
 
   # Make sure we don't break Twisted or urllib3
@@ -81,6 +90,7 @@
   - env: TOXENV=py35-cryptographyMaster
   - env: TOXENV=py36-cryptographyMaster
   - env: TOXENV=pypy-cryptographyMaster
+  - env: TOXENV=pypy3-cryptographyMaster
 
 
 install:
@@ -96,16 +106,6 @@
       python get-pip.py --user
       python -m pip install --user virtualenv
     else
-      # install our own pypy. This can be removed if and when Travis gets a reasonably up to date pypy
-      if [[ "${TOXENV}" = pypy* ]]; then
-          rm -rf ~/.pyenv
-          git clone --depth=1 https://github.com/yyuu/pyenv.git ~/.pyenv
-          PYENV_ROOT="$HOME/.pyenv"
-          PATH="$PYENV_ROOT/bin:$PATH"
-          eval "$(pyenv init -)"
-          pyenv install pypy-5.4.1
-          pyenv global pypy-5.4.1
-      fi
       pip install virtualenv
     fi
     python -m virtualenv ~/.venv
@@ -125,12 +125,6 @@
         export PATH="/usr/local/opt/openssl/bin:$PATH"
       fi
     fi
-    # activate the pypy env we installed via our custom pyenv in the install stage
-    if [[ "${TOXENV}" == "pypy" ]]; then
-        PYENV_ROOT="$HOME/.pyenv"
-        PATH="$PYENV_ROOT/bin:$PATH"
-        eval "$(pyenv init -)"
-    fi
     openssl version
     ~/.venv/bin/tox -v
 
diff --git a/tox.ini b/tox.ini
index cbf6693..48cd08e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = {pypy,py27,py34,py35,py36}{,-cryptographyMaster,-cryptographyMinimum},py27-twistedMaster,pypi-readme,check-manifest,flake8,docs,coverage-report
+envlist = {pypy,pypy3,py27,py34,py35,py36}{,-cryptographyMaster,-cryptographyMinimum},py27-twistedMaster,pypi-readme,check-manifest,flake8,docs,coverage-report
 
 [testenv]
 whitelist_externals =