travis: Properly cache and error on timeout

doc/README.md

@@ -57,7 +57,6 @@ The Bitcoin repo's [root README](/README.md) contains relevant information on th
 - [Source Code Documentation (External Link)](https://dev.visucore.com/bitcoin/doxygen/)
 - [Translation Process](translation_process.md)
 - [Translation Strings Policy](translation_strings_policy.md)
-- [Travis CI](travis-ci.md)
 - [JSON-RPC Interface](JSON-RPC-interface.md)
 - [Unauthenticated REST Interface](REST-interface.md)
 - [Shared Libraries](shared-libraries.md)