Clean up DigitalOcean.hs warnings

Signed-off-by: Ricky Elrod <ricky@elrod.me>
Make travis check hlint too

Signed-off-by: Ricky Elrod <ricky@elrod.me>
Fix hlint warnings

Signed-off-by: Ricky Elrod <ricky@elrod.me>
Compile with -Wall

Signed-off-by: Ricky Elrod <ricky@elrod.me>
Fix -Wall warnings in main.hs, but a bunch remain in Digitalocean.hs

Signed-off-by: Ricky Elrod <ricky@elrod.me>