Remove a whole bunch of Travis things

nox · nox · commit 2c8efb9e987f · 2016-09-01T16:03:10.000+02:00
Seems to me like the culprit about the outdated OS X and cmake not being installed
comes from the requested useless sudo support.
diff --git a/.travis.yml b/.travis.yml
@@ -1,7 +1,4 @@
 language: rust
-sudo: 9000
-dist: trusty
-osx_image: xcode7
 rust:
   - nightly
 os:
