Lock `phantomjs-prebuilt` @ v2.1.12 which will lock the `phantomjs` binary to `2.1.1`.

doc/prepare.md

@@ -33,7 +33,7 @@ brew tap homebrew/dupes
 brew tap homebrew/versions
 brew install git redis postgresql libiconv icu4c pkg-config cmake nodejs go openssl node npm
 bundle config build.eventmachine --with-cppflags=-I/usr/local/opt/openssl/include
-npm install phantomjs-prebuilt -g
+npm install phantomjs-prebuilt@2.1.12 -g
 ```
 ### Ubuntu
@@ -47,7 +47,7 @@ sudo apt-get install software-properties-common python-software-properties
 sudo apt-add-repository -y ppa:ubuntu-lxc/lxd-stable
 sudo apt-get update
 sudo apt-get install git postgresql postgresql-contrib libpq-dev redis-server libicu-dev cmake g++ nodejs libkrb5-dev golang ed pkg-config
-npm install phantomjs-prebuilt -g
+npm install phantomjs-prebuilt@2.1.12 -g
 ```
 ### Arch Linux
@@ -56,7 +56,7 @@ Please read [the prerequisites for all platforms](#prerequisites-for-all-platfor
 ```
 pacman -S postgresql redis postgresql-libs icu nodejs ed cmake openssh git go
-npm install phantomjs-prebuilt -g
+npm install phantomjs-prebuilt@2.1.12 -g
 ```
 ### Debian