Custom indentation can be specified in the Gruntfile

Previously the require config file would be updated using 4 spaces for
indentation.

Now the indentation value can optionally be added to the Gruntfile.

If no indent value is specifed the default of 4 spaces will be used.
Merge pull request #4 from ashiguruma/custom-indentation-value

Custom indentation can be specified in the Gruntfile
Update deps
Update test
0.2.0