google-api-go-generator: increase range of cleanPathString to include "-" rune.
google-api-go-generator: increase range of cleanPathString to include "-" rune.

R=bradfitz
CC=golang-dev
http://codereview.appspot.com/6348083

Committer: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

bpo/google-api-go-client,bpo/google-api-go-client