[epiphany] Update README.md

[Michael Catanzaro <mcatanzaro src gnome org>]

commit a1d6c75bf1dd9c0e761555506fedb8212beebf12
Author: Michael Catanzaro <mcatanzaro posteo net>
Date:   Sun Jul 22 20:54:19 2018 +0000

    Update README.md

 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/README.md b/README.md
index ab0872805..52952ac15 100644
--- a/README.md
+++ b/README.md
@@ -29,7 +29,7 @@ Epiphany the same way you would any software that uses Meson. For example:
 $ mkdir build && cd build
 $ meson ..
 $ ninja
-$ ninja install
+$ sudo ninja install
 ```
 
 Meson is the best build system.