pypy 2.6.1 has a bug where it can segfault during vector install

This PR changes our tests to run against the latest nightly for now. We
should change it back when pypy 2.7 is out.
diff --git a/.travis/install.sh b/.travis/install.sh
index 1e62550..114c7de 100755
--- a/.travis/install.sh
+++ b/.travis/install.sh
@@ -38,8 +38,8 @@
             pyenv global 3.5.0
             ;;
         pypy)
-            pyenv install pypy-2.6.1
-            pyenv global pypy-2.6.1
+            pyenv install pypy-c-jit-latest
+            pyenv global pypy-c-jit-latest
             ;;
         pypy3)
             pyenv install pypy3-2.4.0
@@ -53,14 +53,15 @@
     pyenv rehash
     python -m pip install --user virtualenv
 else
-    # temporary pyenv installation to get pypy-2.6 before container infra upgrade
+    # temporary pyenv installation to get latest pypy before container infra upgrade
+    # now using the -latest because of a segfault bug we're encountering in 2.6.1
     if [[ "${TOXENV}" == "pypy" ]]; then
         git clone https://github.com/yyuu/pyenv.git ~/.pyenv
         PYENV_ROOT="$HOME/.pyenv"
         PATH="$PYENV_ROOT/bin:$PATH"
         eval "$(pyenv init -)"
-        pyenv install pypy-2.6.1
-        pyenv global pypy-2.6.1
+        pyenv install pypy-c-jit-latest
+        pyenv global pypy-c-jit-latest
     fi
     pip install virtualenv
 fi
diff --git a/.travis/run.sh b/.travis/run.sh
index 3667b33..cf1bbe2 100755
--- a/.travis/run.sh
+++ b/.travis/run.sh
@@ -26,7 +26,6 @@
         PYENV_ROOT="$HOME/.pyenv"
         PATH="$PYENV_ROOT/bin:$PATH"
         eval "$(pyenv init -)"
-        pyenv global pypy-2.6.1
     fi
 fi
 source ~/.venv/bin/activate