[emacs] Add ein package.

install-packages.el

@@ -34,6 +34,7 @@
 (package-install 'dash)
 (package-install 'dash-functional)
 (package-install 'diffview)
+(package-install 'ein)
 (package-install 'elpy)
 (package-install 'fish-mode)
 (package-install 'flycheck)