Update README.md

Author: jasonkarns

README.md

@@ -19,13 +19,15 @@ To install, clone this repository into your `$(nodenv root)/plugins` directory.
 
     $ brew install nodenv/nodenv/node-build-update-defs
 
-*Requires manually adding `$(brew --prefix node-build-update-defs)/share/node-build` directory to `NODE_BUILD_DEFINITIONS`*
+*__Note:__
+Requires manually adding `$(brew --prefix node-build-update-defs)/share/node-build` directory to `NODE_BUILD_DEFINITIONS`*
 
 ### Installation with npm
 
     $ npm install --global @nodenv/node-build-update-defs
 
-*Requires manually adding `$(npm -g prefix)/lib/node_modules/@nodenv/node-build-update-defs/share/node-build` directory to `NODE_BUILD_DEFINITIONS`*
+*__Note:__
+Requires manually adding `$(npm -g prefix)/lib/node_modules/@nodenv/node-build-update-defs/share/node-build` directory to `NODE_BUILD_DEFINITIONS`*
 
 ## Requirements