Pin dependencies and update vendors

vendor/github.com/mattn/go-isatty/.travis.yml

@@ -2,6 +2,10 @@ language: go
 go:
   - tip
 
+os:
+  - linux
+  - osx
+
 before_install:
   - go get github.com/mattn/goveralls
   - go get golang.org/x/tools/cmd/cover

vendor/github.com/mattn/go-isatty/isatty_others.go

@@ -3,7 +3,7 @@
 
 package isatty
 
-// IsCygwinTerminal() return true if the file descriptor is a cygwin or msys2
+// IsCygwinTerminal return true if the file descriptor is a cygwin or msys2
 // terminal. This is also always false on this environment.
 func IsCygwinTerminal(fd uintptr) bool {
 	return false