listed grunt as tool, renamed sections

Correct. There is no need to request the manual installation of `grunt` by the user as in the [amber-examples/package.json](https://github.com/amber-smalltalk/amber-examples/blob/master/package.json) file it is specified that `amber-examples` need `grunt`. This is done with the `devDependencies` attribute.

    "devDependencies": {
        "grunt": "~0.4.0",
        "amber-dev": "~0.1.1"
      }

I had moved `grunt` to the **Tools needed** section because [this earlier version](https://github.com/amber-smalltalk/amber-examples/commit/0794e4daabfa7732687f617899b7191089003c4d#diff-04c6e90faac2675aa89e2176d2eec7d8) of the README file explicitly requested grunt to be installed manually

**Conclusion:** remove the request for the manual installation of `grunt`.