Option to write render_html or render_latex output to a file

[MaxGhenis]

This is especially helpful for render_latex, since a common workflow is to store each tex component as separate files, and then include them in the master tex file. It'd be nice to have a render_latex(out='out.tex') option.

Current workaround (which would probably be the way to implement the feature) is:

f = open("out.tex", "w")
f.write(stargazer.render_latex())
f.close()

[toobaz]

Current workaround (which would probably be the way to implement the feature) is:

Just for the records, you can spare one line:

with open("out.tex", "w") as f:
    f.write(stargazer.render_latex())

... but sure, this would be nice to have.