fixed github directory match pattern

The regexp "[a-z0-9A-Z_.\-/]" is strict , not match dir
with space(issue #293) or other special character.
change it to "[^/]" matching more directories in github repo URL.

fixed #293

gosrc/github.go

diff --git a/gosrc/github.go b/gosrc/github.go
index b612346..181d938 100644
--- a/gosrc/github.go
+++ b/gosrc/github.go
@@ -18,7 +18,7 @@
 
 func init() {
 	addService(&service{
-		pattern:         regexp.MustCompile(`^github\.com/(?P<owner>[a-z0-9A-Z_.\-]+)/(?P<repo>[a-z0-9A-Z_.\-]+)(?P<dir>/[a-z0-9A-Z_.\-/]*)?$`),
+		pattern:         regexp.MustCompile(`^github\.com/(?P<owner>[a-z0-9A-Z_.\-]+)/(?P<repo>[a-z0-9A-Z_.\-]+)(?P<dir>/[^/]*)?$`),
 		prefix:          "github.com/",
 		get:             getGitHubDir,
 		getPresentation: getGitHubPresentation,