Print errors using default format
Refactor API fetch method

* tighten scope of structs
* remove unnecessary pointer
* introduce pernicious returns
* remove unnecessary assert
One folder to rule them all.

* Inline all the files into the project directory.
* Get rid of `src`.
* Use `go get` for dependencies.
* Make build scripts work.
* Update README with new requirements/instructions.
Add go get to Travis config
Tweak Travis config