Convert extensions to recipes

[gustaphe]

I've wanted to do this for a while, and it recently became much easier. Low priority, but maybe at least worth keeping in mind if we ever need to change either extension.

If this breaks something, that something was not in the tests.

[codecov]

Codecov Report

Patch coverage: 75.00% and project coverage change: -0.26 ⚠️

Comparison is base (1dcae2c) 82.38% compared to head (78290b1) 82.12%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #263      +/-   ##
==========================================
- Coverage   82.38%   82.12%   -0.26%     
==========================================
  Files          21       21              
  Lines         829      817      -12     
==========================================
- Hits          683      671      -12     
  Misses        146      146              

Impacted Files	Coverage Δ
ext/SymEngineExt.jl	50.00% <50.00%> (-30.00%)	⬇️
ext/DataFramesExt.jl	83.33% <83.33%> (-10.00%)	⬇️

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[rodrigomha]

@gustaphe A quick question here. What is now the intended form to use create a markdown table from a Dataframe now that mdtable(DataFrame) is not supported directly? This broke some of my documentation and required to fix Latexify in 0.16.3 for now.

Thanks

[gustaphe]

That is unfortunate, we should have had a test for that.
I'm not currently at my computer, but latexify(df) or latexify(df; env=:mdtable) should do the same thing.