Fixing compilation issue, and library formatting

During installation:

```go
ivolo:Desktop ivolo$ go get github.com/segmentio/analytics-go
# github.com/segmentio/analytics-go
../dev/src/github.com/segmentio/analytics-go/analytics.go:70: too many arguments in call to uuid.SwitchFormat
```

`uuid.SwitchFormat` seems to have changed signature, so we're removing the second argument, per their [docs](http://godoc.org/github.com/twinj/uuid#SwitchFormat).

Also, `library` should be an object with "name" and "version" so made that change as well.

/cc @visionmedia