[skip ci] Update docs and build badges for the Travis -> Cirrus move

CONTRIBUTING.md

@@ -76,21 +76,21 @@ add a test that would have failed without the fix.
 
 After you've made your change, make sure the tests pass in your development
 environment. We also have [continuous integration set up on
-Travis-CI][travis-ci], which might find some issues on other platforms. The CI
+Cirrus-CI][cirrus-ci], which might find some issues on other platforms. The CI
 will run once you open a pull request.
 
 There is also infrastructure for running tests for other targets
 locally.  More information is available in the [CI Readme][ci-readme].
 
-[travis-ci]: https://travis-ci.org/nix-rust/nix
+[cirrus-ci]: https://cirrus-ci.com/github/nix-rust/nix
 [ci-readme]: ci/README.md
 
 ### Disabling a test in the CI environment
 
 Sometimes there are features that cannot be tested in the CI environment.
-To stop a test from running under CI, add `#[cfg_attr(travis, ignore)]`
-to it. Please include a comment describing the reason it shouldn't run
-under CI, and a link to an upstream issue if possible!
+To stop a test from running under CI, add `skip_if_cirrus!()` to it. Please
+describe the reason it shouldn't run under CI, and a link to an issue if
+possible!
 
 ## bors, the bot who merges all the PRs
 

Cargo.toml

@@ -9,7 +9,7 @@ license     = "MIT"
 categories  = ["os::unix-apis"]
 exclude     = [
   "/.gitignore",
-  "/.travis.yml",
+  "/.cirrus.yml",
   "/ci/*",
   "/Cross.toml",
   "/RELEASE_PROCEDURE.md",

README.md

@@ -1,6 +1,5 @@
 # Rust bindings to *nix APIs
 
-[![Travis Build Status](https://travis-ci.org/nix-rust/nix.svg?branch=master)](https://travis-ci.org/nix-rust/nix)
 [![Cirrus Build Status](https://api.cirrus-ci.com/github/nix-rust/nix.svg)](https://cirrus-ci.com/github/nix-rust/nix)
 [![crates.io](http://meritbadge.herokuapp.com/nix)](https://crates.io/crates/nix)
 

bors.toml

@@ -1,4 +1,3 @@
-# Gate on Travis CI and Buildbot
 status = [
   "FreeBSD amd64 & i686",
   "OSX x86_64",
@@ -34,10 +33,10 @@ status = [
 # Set bors's timeout to 1 hour
 #
 # bors's timeout should always be at least twice as long as the test suite
-# takes.  This is to allow Travis to fast-fail a test; if one of the builders
-# immediately reports a failure, then bors will move on to the next batch,
-# leaving the slower builders to work through the already-doomed run and the
-# next one.
+# takes.  This is to allow the CI provider to fast-fail a test; if one of the
+# builders immediately reports a failure, then bors will move on to the next
+# batch, leaving the slower builders to work through the already-doomed run and
+# the next one.
 #
 # At the time this was written, nix's test suite took about twenty minutes to
 # run.  The timeout was raised to one hour to give nix room to grow and time