updated main to use _gen.go imports for typewriters, build in a temp
folder, and clean up.
uses panic so it cleans up properly
Update main.go
adding comments, fixing tests
fixing []byte for file
fixing error for no _gen.go
Merge branch 'typewriter' of github.com:wfreeman/gen into typewriter
use tempdir; go run instead of go build + exec; no need to record if dir created
renames & gen'd files