Use custom Hamcrest matchers for assertion behavior

[tiesebarrell]

Re-write internal assertions to use custom Hamcrest matchers. These can later be exposed as an alternative to the static methods on ProcessAssert.

Resource: http://www.slideshare.net/wakaleo/junit-kung-fu-getting-more-out-of-your-unit-tests.

[tiesebarrell]

Entry point classes example: https://joel-costigliola.github.io/assertj/assertj-assertions-generator.html#generated-entry-points