Peer authentication failed for user "miningcore"
Trying to get this running on Ubuntu 16.04 64bit.

When doing this step:

`psql -d miningcore -U miningcore -f createdb.sql`

I get the following error: `psql: FATAL:  Peer authentication failed for user "miningcore"`

Unfortunately I'm not at all familaiar with Postgresl....I've seen people talk about switching to an md5 authentication method but have no idea how to do this.

Any thoughts?
