Update nix requirement from ^0.11 to ^0.14

[dependabot-preview]

Updates the requirements on nix to permit the latest version.

Changelog

Sourced from nix's changelog.

[0.14.0] - 2019-05-21

Added

• Add IP_RECVIF & IP_RECVDSTADDR. Enable IP_PKTINFO and IP6_PKTINFO on netbsd/openbsd.
  (#1002)
• Added inotify_init1, inotify_add_watch and inotify_rm_watch wrappers for
  Android and Linux. (#1016)
• Add ALG_SET_IV, ALG_SET_OP and ALG_SET_AEAD_ASSOCLEN control messages and AF_ALG
  socket types on Linux and Android (#1031)
• Add killpg
  (#1034)
• Added ENOTSUP errno support for Linux and Android.
  (#969)
• Add several errno constants from OpenBSD 6.2
  (#1036)
• Added from_std and to_std methods for sys::socket::IpAddr
  (#1043)
• Added nix::unistd:seteuid and nix::unistd::setegid for those platforms that do
  not support setresuid nor setresgid respectively.
  (#1044)
• Added a access wrapper
  (#1045)
• Add forkpty
  (#1042)
• Add sched_yield
  (#1050)

Changed

• PollFd event flags renamed to PollFlags (#1024)

• recvmsg now returns an Iterator over ControlMessageOwned objects rather
  than ControlMessage objects. This is sadly not backwards-compatible. Fix
  code like this:

  if let ControlMessage::ScmRights(&fds) = cmsg {

  By replacing it with code like this:

  if let ControlMessageOwned::ScmRights(fds) = cmsg {

  (#1020)

• Replaced CmsgSpace with the cmsg_space macro.
  (#1020)

Fixed

• Fixed multiple bugs when using sendmsg and recvmsg with ancillary control messages
  (#1020)
• Macros exported by nix may now be imported via use on the Rust 2018
  edition without importing helper macros.
  (#1041)

... (truncated)

Commits

• fdc4b46 Merge #1061
• 15dd6c1 Release v0.14.0
• 1135b64 Merge #1050
• 0a7adb1 [skip ci] add missing CHANGELOG entry for PR #1055
• 06d7463 Merge #1054
• 45ec8fc Implement sched_yield.
• b33f273 Remove a redundant "use libc"
• 434b866 Merge #1055
• 196b05b Fix build on arm and s390x after recent libc changes
• 63aec50 Merge #1048
• Additional commits viewable in compare view

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[dependabot-preview]

Superseded by #11.