Move go to src folder, pre-commit hook

[leonklingele]

As discussed in #61, this PR

• separates the Go code from the rest of the project by moving it to a src/ folder
• adds a pre-commit hook to run tests and go fmt before a change can be commited

[leonklingele]

As soon as #48 is merged, I will also run go vet in the pre-commit hook.
This will greatly improve the code quality / standard conformity.

[leonklingele]

On my machine, the pre-commit hook checks currently take about 3 seconds.
We need to find a way to cut this down.

[bndw]

Once you rebase and this is merged, I've got a local branch that speeds up those tests.

[bndw]

#66 Should make the pre-commit hook bearable.

[leonklingele]

Rebased.

[bndw]

LGTM

EDIT
Moving forward, PRs should be opened against the develop branch #69