Added PHP 7.3 builds - updated Travis CI configuration

[michalbundyra]

No description provided.

[weierophinney]

This repository has been closed and moved to laminas-api-tools/api-tools-rpc; a new issue has been opened at laminas-api-tools/api-tools-rpc#1.

[weierophinney]

This repository has been moved to laminas-api-tools/api-tools-rpc. If you feel that this patch is still relevant, please re-open against that repository, and reference this issue. To re-open, we suggest the following workflow:

• Squash all commits in your branch (git rebase -i origin/{branch})
• Make a note of all changed files (`git diff --name-only origin/{branch}...HEAD
• Run the laminas/laminas-migration tool on the code.
• Clone laminas-api-tools/api-tools-rpc to another directory.
• Copy the files from the second bullet point to the clone of laminas-api-tools/api-tools-rpc.
• In your clone of laminas-api-tools/api-tools-rpc, commit the files, push to your fork, and open the new PR.
  We will be providing tooling via laminas/laminas-migration soon to help automate the process.