Add Matrix Build Support to Travis-CI Integration

[ryanRfox]

User Story
As a Core Developer I want my code changes tested against multiple platforms and dependency versions so that I receive feedback when a code change fails within the build matrix.

Additional Context (optional)
Currently we use Travis-CI for automated builds on all branches. Currently the /.travis.yml file only targets Linux (Ubuntu Trusty) and the default dependencies from apt for that version. Travis-CI has the concept of a Build Matrix. The desire is to define a build matrix to cover versions of Boost [1.57 - 1.65.1], OpenSSL [1.0 - 1.1], Compilers [gcc, clang] and platforms [Ubuntu, OSX].

Note: We are open to using other automated build services and adding support for the Windows platform. However, both are out of scope for this Issue (Windows not supported by Travis-CI at this time).

CORE TEAM TASK LIST

• Evaluate / Prioritize Feature Request
• Refine User Stories / Requirements
• Define Test Cases
• Design / Develop Solution
  • Assigned: @marcialvieira
  • Estimated: 10 hours
• Perform QA/Testing
• Update Documentation

[marcialvieira]

Hi @ryanRfox and everyone, I'm interested in working on this issue as a continuation of #958

[ryanRfox]

Outstanding! You will be our go-to build guy ;) I'm assigning @marcialvieira and will await an estimate from you.

[cogutvalera]

@marcialvieira welcome ! This will be cool when will be done !

[pmconrad]

Need to think about available resources on travis. Perhaps restrict this to main branches only, not PR's nor feature branches.

[abitmore]

Obsolete by #2062 and following changes. Our main CI process is now on Github Actions.