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/golang.org/x/sys/unix/syscall_openbsd.go

@@ -204,6 +204,7 @@ func Uname(uname *Utsname) error {
 //sys	Fchdir(fd int) (err error)
 //sys	Fchflags(fd int, flags int) (err error)
 //sys	Fchmod(fd int, mode uint32) (err error)
+//sys	Fchmodat(dirfd int, path string, mode uint32, flags int) (err error)
 //sys	Fchown(fd int, uid int, gid int) (err error)
 //sys	Flock(fd int, how int) (err error)
 //sys	Fpathconf(fd int, name int) (val int, err error)
@@ -221,6 +222,7 @@ func Uname(uname *Utsname) error {
 //sysnb	Getppid() (ppid int)
 //sys	Getpriority(which int, who int) (prio int, err error)
 //sysnb	Getrlimit(which int, lim *Rlimit) (err error)
+//sysnb	Getrtable() (rtable int, err error)
 //sysnb	Getrusage(who int, rusage *Rusage) (err error)
 //sysnb	Getsid(pid int) (sid int, err error)
 //sysnb	Gettimeofday(tv *Timeval) (err error)
@@ -258,6 +260,7 @@ func Uname(uname *Utsname) error {
 //sysnb	Setresgid(rgid int, egid int, sgid int) (err error)
 //sysnb	Setresuid(ruid int, euid int, suid int) (err error)
 //sysnb	Setrlimit(which int, lim *Rlimit) (err error)
+//sysnb	Setrtable(rtable int) (err error)
 //sysnb	Setsid() (pid int, err error)
 //sysnb	Settimeofday(tp *Timeval) (err error)
 //sysnb	Setuid(uid int) (err error)
@@ -306,7 +309,6 @@ func Uname(uname *Utsname) error {
 // getlogin
 // getresgid
 // getresuid
-// getrtable
 // getthrid
 // ktrace
 // lfs_bmapv
@@ -342,7 +344,6 @@ func Uname(uname *Utsname) error {
 // semop
 // setgroups
 // setitimer
-// setrtable
 // setsockopt
 // shmat
 // shmctl