WIP: Remove Boost as a required dependency

[arcuru]

After one too many issues with people having trouble installing Boost, I created this to get feedback about removing it as a required dependency, primarily by switching to a header-only unit testing suite.

This closes every open bug in the repo (adding the tags here for auto-closing)
(closes #96, closes #116, closes #123, closes #126, closes #149, closes #150)

The primary goal was to remove Boost as a default dependency, though some tests might still require it. This change removes it from everywhere except for the meetup test, as that's already a nightmare of a test.

This moves to using Catch for testing, because as far as I can tell that is the most popular header-only unit testing suite for C++ (I have no stake in this, I've never used it before). This allows us to bundle the test suite along with the problems, so there are no dependencies other than a C++11 compliant compiler and some toolchain (CMake + Make, or almost any IDE can work with the files directly).

For the majority of problems, this just involved replacing the Boost.Test macros with their Catch equivalents, but a handful of problems have more substantial changes:

• gigasecond is the most heavily impacted test, and is a breaking change for existing solutions. It used boost::posix_time across the user interface so I rewrote the interface to use strings, the example to use <ctime>, and increased the difficulty. It should at some point be re-ordered later in the track.
• robot-names used Boost.Regex to validate the user supplied names in the test suite. I attempted to replace this with std::regex, but due to issues on Travis-CI (that I wasn't able to reproduce with the same toolchain outside Travis) I just rewrote the validation to avoid regex. Ideally this should just use std::regex, but I didn't want to spend more time debugging it for a test that's just a one-liner if statement. See 1ff8dba
• anagram, bob, crypto-square, and word-count all used Boost libs in the example solutions (that was not user visible in the test suites). I removed those in change 8922c1f, but I don't consider those changes to be too important, since they are not user visible.

Documentation has not yet been updated, but will be if there's support for this change.

[DonBarredora]

Is this ready to be merged into the master branch?

[LegalizeAdulthood]

I think it would need to coincide with a big docs update. Is that correct, Patrick?

[pacmancoder]

Bump. @LegalizeAdulthood, @jackhughesweb

I think this issue should solved, as exercism should teach how to use C++ according to its modern standard. I think that all code, which use Boost should be replaced with corresponding stl-based.

I can dig into this issue and update exercises.
By the way, I think Gigasecond should use modern std::chrono, not ctime after refactoring.

So, how can I help with this issue? @patricksjackson, can I cooperate with you somehow to continue work on this PR?

[arcuru]

Sorry for the delay here, I assumed somebody would've finished this change without me in the past yearish this has been open. I had to step away for a little while for various reasons, but I have a little time now to help out and clean up around here.

I will be taking another look at this and updating it for merge over the next few weeks.

@pacmancoder or others, if you would like to help please open a PR against this branch. (This is tracked as another branch in this repo, so you can checkout this branch and make a PR targeting it. If not you can comment here with a pointer to your change and I can pull the commit).

This will be a big change, as all the Docs need to be updated as well. I will probably need help for testing it at the very least. I'll update here and/or make a tracking issue to track everything that needs to happen and how you could help.

[arcuru]

Deprecating this, using #233 to track the work needed to incrementally move to Catch.