cmd/fiximports: added package-level documentation
cmd/fiximports: added package-level documentation

Change-Id: I612229e5d9e80a25cd77296c0abb6bdcf62bcf8a
Reviewed-on: https://go-review.googlesource.com/12924
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

glasser/golang-tools,golang/tools,springning/tools,cmars/tools,argandas/tools,matryer/tools,cmars/tools,josharian/tools,glasser/golang-tools,matryer/tools,jdhenke/tools,syreclabs/go-tools,josharian/tools,syreclabs/go-tools,jdhenke/tools,golang/tools,jdhenke/tools,cw2018/tools,glasser/golang-tools,magiccao/tools,josharian/tools,runcom/tools,glasser/golang-tools,syreclabs/go-tools,nicot/tools,cw2018/tools,runcom/tools,runcom/tools,jdhenke/tools,magiccao/tools,syreclabs/go-tools,nicot/tools,argandas/tools,cw2018/tools,syreclabs/go-tools,cmars/tools,magiccao/tools,matryer/tools,argandas/tools,syreclabs/go-tools,argandas/tools,springning/tools,runcom/tools,golang/tools,golang/tools,springning/tools,matryer/tools,magiccao/tools,nicot/tools,nicot/tools,springning/tools,cmars/tools,josharian/tools,golang/tools,cw2018/tools