Permission error when installing

[Peter]

Whithout sudo, npm install -g spec-md

npm WARN checkPermissions Missing write access to /usr/local/lib
/usr/local/lib
└─┬ spec-md@0.4.8 
  └── highlight.js@9.11.0 

npm ERR! Linux 4.4.0-78-generic
npm ERR! argv "/usr/bin/nodejs" "/usr/bin/npm" "install" "-g" "spec-md"
npm ERR! node v4.2.6
npm ERR! npm  v3.5.2
npm ERR! path /usr/local/lib
npm ERR! code EACCES
npm ERR! errno -13
npm ERR! syscall access

npm ERR! Error: EACCES: permission denied, access '/usr/local/lib'
npm ERR!     at Error (native)
npm ERR!  { [Error: EACCES: permission denied, access '/usr/local/lib']
npm ERR!   errno: -13,
npm ERR!   code: 'EACCES',
npm ERR!   syscall: 'access',
npm ERR!   path: '/usr/local/lib' }
npm ERR! 
npm ERR! Please try running this command again as root/Administrator.

npm ERR! Please include the following file with any support request:
npm ERR!     /home/user/sandbox/npm-debug.log

[Lee Byron]

This is an issue with your local machine, not with this library. I suggest you do some web searches for how to solve this issue with permissions.