Integrate a tool for catching missing includes

[sssoleileraaa]

Let's integrate a tool such as:

• https://include-what-you-use.org
• http://clang.llvm.org/extra/include-fixer.html
• https://github.com/google/styleguide/tree/gh-pages/cpplint

to catch missing includes that might not appear until Travis tries to build your code for a different OS, see https://travis-ci.org/mapbox/node-cpp-skel/builds/394326432 for example and notice how this builds for macOS but not Linux (this was due to missing #include <memory>).

Referencing @springmeyer's comment and tool suggestions here: #129 (comment)