Converting to 4 spaces

This was causing some errors in JSHint (based on your .jshintrc):

```
$ grunt
Running "jshint:files" (jshint) task

Chapter-1/Gruntfile.js
  line 0   col 0  ES5 option is now set per default
  line 4   col 3  Expected 'require' to have an indentation at 5 instead at 3.
  line 6   col 3  Expected 'var' to have an indentation at 5 instead at 3.
  line 8   col 3  Expected 'grunt' to have an indentation at 5 instead at 3.
  line 10  col 3  Expected 'var' to have an indentation at 5 instead at 3.
  line 12  col 3  Expected 'grunt' to have an indentation at 5 instead at 3.

Chapter-1/src/scripts/main.js
  line 0   col 0  ES5 option is now set per default
  line 2   col 5  Missing "use strict" statement.
  line 1   col 1  '$' is not defined.
  line 2   col 5  '$' is not defined.

✖ 10 problems

Warning: Task "jshint:files" failed. Use --force to continue.

Aborted due to warnings.
```