How to execute 'coffee' command after installation?

I installed coffee-script as per directions.

$ npm install http://github.com/jashkenas/coffee-script/tarball/master
npm http GET http://github.com/jashkenas/coffee-script/tarball/master   
npm http 200 http://github.com/jashkenas/coffee-script/tarball/master
npm http GET https://registry.npmjs.org/mkdirp
npm http 200 https://registry.npmjs.org/mkdirp
npm WARN package.json cookie-signature@1.0.0 No repository field.
npm WARN package.json fresh@0.1.0 No repository field.
npm WARN package.json methods@0.0.1 No repository field.
npm WARN package.json range-parser@0.0.4 No repository field.
npm WARN package.json send@0.1.0 No repository field.
npm WARN package.json ms@0.1.0 No repository field.
npm WARN package.json pause@0.0.1 No repository field.
npm WARN package.json bytes@0.2.0 No repository field.
npm WARN package.json formidable@1.0.11 No repository field.
npm WARN package.json css@1.0.8 No repository field.
npm WARN package.json uglify-js@2.2.5 'repositories' (plural) Not supported.
npm WARN package.json Please pick one as the 'repository' field
npm WARN package.json walk@2.2.1 No repository field.   
npm WARN package.json css-parse@1.0.4 No repository field.
npm WARN package.json css-stringify@1.0.5 No repository field.
coffee-script@1.6.3 node_modules/coffee-script
└── mkdirp@0.3.5

yet when i execute 'coffee' command i get

$ coffee
-bash: coffee: command not found

What am i doing wrong?

PS: i am doing this on Mac Terminal

EDIT: -

Same problem is occurs when i install nodemon the npm install takes place similar to above. But when i input a nodemon command on $ prompt it says -bash: nodemon: command not found

I installed coffeescript on my mac yeasterday as a matter of fact. Here is how I did it:

First of all, go install NodeJS.

Then go in Terminal and type the following: sudo npm install -g coffee-script

That's it - If you type in coffee in Terminal, it should start without a problem

Anything you want to run as a command (nodemon, coffee, node-inspector) must be installed with npm install -g the-package-name. If you use npm install it just puts it into your local node_modules directory and won't create the symlink for command line execution.

If you find that you need to use sudo, you might want to read this blog post: http://howtonode.org/introduction-to-npm:

what, no sudo?

I strongly encourage you not to do package management with sudo! Packages can run arbitrary scripts, which makes sudoing a package manager command as safe as a chainsaw haircut. Sure, it's fast and definitely going to cut through any obstacles, but you might actually want that obstacle to stay there.

I recommend doing this once instead:

sudo chown -R $USER /usr/local