Fix potential typo in README (#348)

diff --git a/README.md b/README.md
index 6d15a91..54e2958 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@
 We recommend the following version constraint:
 
     dependencies:
-      quiver: '>=0.25.0<0.26.0'
+      quiver: '>=0.25.0 <0.26.0'
 
 # Main Libraries