Use grunt and bower packages as local dependencies

What this PR proposes:
* Use `grunt-bower-task` package to get control of bower modules
* Remove `grunt-cli` and `bower` global dependencies (bower as local package corresponds with previous item). Wait, global packages as local ones? It's not supported! It's confusing! It's not recommended! It's madness! Turn's out, it's perfectly <a href="https://npmjs.org/doc/misc/npm-scripts.html#path">fine</a>.
* Add `build` command to `package.json`, so jQuery could be builded with one command, but don't forget to emphasizes about `grunt` commands as a preferable way to work with jQuery 
* Update readme to reflect these changes

/cc @timmywil