Render examples in docs

[theogf]

Solves #91

This uses our own in-house JuliaGPsDocs package to render every example nicely!

[coveralls]

Pull Request Test Coverage Report for Build 4481014037

Warning: This coverage report may be inaccurate.

We've detected an issue with your CI configuration that might affect the accuracy of this pull request's coverage report.
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A quick fix for this PR: rebase it; your next report should be accurate.

• 7 of 8 (87.5%) changed or added relevant lines in 1 file are covered.
• 6 unchanged lines in 1 file lost coverage.
• Overall coverage remained the same at 87.394%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/gp/lti_sde.jl	7	8	87.5%

Files with Coverage Reduction	New Missed Lines	%
src/gp/lti_sde.jl	6	95.43%

Totals
Change from base Build 4480603537:	0.0%
Covered Lines:	1241
Relevant Lines:	1420

---

💛 - Coveralls

[theogf]

Given this mention of signal (15), I would assume we reach a memory limit when running all examples in parallel... I will try to limit the number of simultaneous processes.

[theogf]

Potential solution: JuliaGaussianProcesses/JuliaGPsDocs.jl#18

[willtebbutt]

Same as other PRs -- I'm having a clear-out. Please re-open if you would like to push further.