Change default to localhost

[domoritz]

We discussed this in the meeting. The reason is that we want local setups to work without having to change the code.

@billhowe

[dhalperi]

Seems reasonable... I guess the question is, what's more common:

• someone checks out myria-web to work on raco, work on features for the website, or something else that would use the production backend.
• someone checks out myria-web to work with their local version of MyriaX
• someone checks out myria-web to work with a new/custom deployment of MyriaX or another backend

Certainly the former case is most common for our group -- only if the myria-web changes necessitate backend changes would someone want to use localhost. Note that the third case will never be well-supported by our default.

I am slightly against this change because it makes myria-web useless on its own, but I don't feel strongly. Feel free to merge if you've consensus.

[domoritz]

The main reason is that we want the myria hello world from the docs to work without code changes. At some point we want a cleaner solution such as a config file or a drop down but for now this was the consensus in the group meeting.