Openzeppelin-contracts: npm install does not create node_modules directory

[ruby32]

Problem

Following the instructions to install zeppelin-solidity, the node_modules directory is not created.

Expected results

The node_modules directory is populated.

Actual results

After running truffle init successfully, running npm install zeppelin-solidity does not return an error, but it does have a ton of warnings:

$ npm install zeppelin-solidity
npm WARN saveError ENOENT: no such file or directory, open '/home/ubuntu/package.json'
npm WARN enoent ENOENT: no such file or directory, open '/home/ubuntu/package.json'
npm WARN [email protected] requires a peer of webpack@^2.0.0 || ^3.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN ubuntu No description
npm WARN ubuntu No repository field.
npm WARN ubuntu No README data
npm WARN ubuntu No license field.

+ [email protected]
updated 1 package in 0.903s
$ ls -l
total 20
drwxrwxr-x 2 ubuntu ubuntu 4096 Nov 17 20:20 contracts
drwxrwxr-x 2 ubuntu ubuntu 4096 Nov 17 20:07 migrations
drwxrwxr-x 2 ubuntu ubuntu 4096 Nov 17 20:07 test
-rw-rw-r-- 1 ubuntu ubuntu  135 Nov 17 20:07 truffle-config.js
-rw-rw-r-- 1 ubuntu ubuntu  135 Nov 17 20:07 truffle.js

The node_modules directory is not created as expected.

System details:

Ubuntu 16.04
npm 5.5.1
nodejs v8.9.1
truffle v4.0.1
zeppelin-solidity 1.3.0

[frangio]

Please see #475. Run npm init before installing.

I will add this to the README. We didn't realize it was missing there.