Build everything again

Restore 'skip_cleanup' (misunderstood deprecation)

Update releases token

Tidy up build markdown file

Add cath-cluster to Travis-CI deployed files

Tweak validator to workaround prob in older GCCs

Workaround old compilers' "call is ambiguous" prob

Add changes missing from previous commit

These changes should have been part of a2d5fa1

Remove valid noexcept spec to workaround GCC 4.9.2

Tweak namespacing issue for GCC 4.9