Adding a mutation example

[jaredonline]

Adds the simple mutation for #60

Left to do:

• add an http based example

[coveralls]

Coverage increased (+3.0%) to 90.543% when pulling f1155e6 on jaredonline:mutation-example into 909ca9f on graphql-go:master.

[coveralls]

Coverage increased (+3.0%) to 90.543% when pulling 48847e3 on jaredonline:mutation-example into 909ca9f on graphql-go:master.

[chris-ramon]

Hi @jaredonline!, thanks a lot for taking the time to work on this! 👍

I'd like to suggest adding this todo mutation example to the existing examples/todo/main.go one.

[jaredonline]

Oh! Nice! I wasn't aware that the mutation example for Todos was already there @chris-ramon. Should I put remove my example entirely and just add the new mutation to the existing todo stuff? Should #60 be closed then?

[chris-ramon]

Should I put remove my example entirely and just add the new mutation to the existing todo stuff?

That would be awesome @jaredonline, so the todo example would keep becoming solid & continue showing important features to lib users.

And yes! this PR would be closing #60.

[chris-ramon]

Closing this one in favor of #189

Thanks for the initial work @jaredonline 👍