Update pypy version regexp to get last release

PyPy changed naming conention since 5.8 release, not it's called
pypy2.7-x.x.x

Author: lopuhin

.travis.yml

@@ -31,7 +31,7 @@ install:
           rm -rf "$PYENV_ROOT" && git clone --depth 1 https://github.com/yyuu/pyenv.git "$PYENV_ROOT"
         fi
         # get latest portable PyPy from pyenv directly (thanks to natural version sort option -V)
-        export PYPY_VERSION=`"$PYENV_ROOT/bin/pyenv" install --list |grep -o -E 'pypy-portable-[0-9][\.0-9]*$' |sort -V |tail -1`
+        export PYPY_VERSION=`"$PYENV_ROOT/bin/pyenv" install --list |grep -o -E 'pypy2.7-portable-[0-9][\.0-9]*$' |sort -V |tail -1`
         "$PYENV_ROOT/bin/pyenv" install --skip-existing "$PYPY_VERSION"
         virtualenv --python="$PYENV_ROOT/versions/$PYPY_VERSION/bin/python" "$HOME/virtualenvs/$PYPY_VERSION"
         source "$HOME/virtualenvs/$PYPY_VERSION/bin/activate"