Fix typo in bigint.go
Add bigint_test.go and bigrat_test.go to GOFILES in Makefile
Regenerate package

- Typo from bigint.go not propagated to bigrat.go

- Readme generated using updated godoc2md and without typo from
  bigint/rat

- bigrat_test: gofmt is happy
Merge pull request #2 from tormoder/master

Regenerate package