Add option to specify 'aliases' file location

[rfgamaral]

I really like the flexibility of this library allowing me to break up my Gruntfile into multiple and more maintainable files. For me, there's only one thing missing and that's the option to specify the aliases file location.

Why would I want this? Well... I like to separate my custom tasks implementation from my tasks configurations and for that I use load-grunt-config like this:

require('load-grunt-config')(grunt, {
    jitGrunt: {
        customTasksDir: path.join(process.cwd(), 'grunt/tasks')
    },
    configPath: path.join(process.cwd(), 'grunt/options')
});

With this configuration, I'm forced to have the aliases file inside the grunt/options folder, which doesn't make much sense to me. It would make more sense to have it in the grunt/tasks folder instead. Or, my preferred option, the root grunt folder as to not mix up with custom tasks and tasks configuration.

[rarila]

:+1:

[AleksueiR]

:+1:

[GwendolenLynch]

:+1:

[jgallen23]

good idea. I'll accept a PR if anybody wants to tackle it