Rewrite pdflatex as a Transform Stream

[kube]

Today pdflatex is meant to be used like this:

pdflatex(latexStream)
pdflatex(latexStream, { texInputs: ['../resources'] })

pdflatex(createReadStream('document.tex')).pipe(createWriteStream('document.pdf'))

After the rewrite it will be used this way:

latexStream.pipe(pdflatex())
latexStream.pipe(pdflatex({ texInputs: ['../resources'] })

createReadStream('document.tex')).pipe(pdflatex()).pipe(createWriteStream('document.pdf'))

[kube]

This should remove some type issues as pdflatex won't need to know exactly the type of the input stream, as it won't take it as argument anymore.