Actually run the book deploy script in CI

The old checks to prevent deploying multiple times ended up making it so we
never deployed because we changed the environment variables we used in CI. This
change means we will deploy multiple times for every push, but this is an
idempotent operation, and makes sure that we won't ever run into the same bug
again.

Author: fitzgen

.travis.yml

@@ -42,8 +42,6 @@ script:
 after_success:
   - test "$TRAVIS_PULL_REQUEST" == "false" &&
     test "$TRAVIS_BRANCH" == "master" &&
-    test "$BINDGEN_FEATURES" == "" &&
-    test "$LLVM_VERSION" == "3.9.0" &&
     ./ci/deploy-book.sh
 
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