vendor: update all dependencies

* Update all dependencies
  * Remove all `[[constraint]]` from Gopkg.toml
  * Add in the minimum number of `[[override]]` to build
  * Remove go get of github.com/inconshreveable/mousetrap as it is vendored
  * Update docs with new policy on constraints

vendor/github.com/sevlyar/go-daemon/lock_file_unix.go

@@ -1,9 +1,8 @@
-// +build dragonfly freebsd linux netbsd openbsd plan9 solaris
+// +build darwin dragonfly freebsd linux netbsd openbsd plan9 solaris
 
 package daemon
 
 import (
-	"fmt"
 	"syscall"
 )
 
@@ -22,19 +21,3 @@ func unlockFile(fd uintptr) error {
 	}
 	return err
 }
-
-const pathMax = 0x1000
-
-func getFdName(fd uintptr) (name string, err error) {
-	path := fmt.Sprintf("/proc/self/fd/%d", int(fd))
-	// We use predefined pathMax const because /proc directory contains special files
-	// so that unable to get correct size of pseudo-symlink through lstat.
-	// please see notes and example for readlink syscall:
-	// http://man7.org/linux/man-pages/man2/readlink.2.html#NOTES
-	buf := make([]byte, pathMax)
-	var n int
-	if n, err = syscall.Readlink(path, buf); err == nil {
-		name = string(buf[:n])
-	}
-	return
-}