Fix go get link

Otherwise on Go 1.2 and Windows
>go get -u -v http://github.com/fiam/gounidecode/unidecode
import "http:/github.com/fiam/gounidecode/unidecode": import path doesn't contain a hostname
package http:/github.com/fiam/gounidecode/unidecode: unrecognized import path "http:/github.com/fiam/gounidecode/unidecode"