Add xtick and ytick in Axis

[jywu20]

Sometimes we need to change the xtick option, for example in this SE question. However, currently xtick is not an optional argument ( MethodError: no method matching Axis(::Array{PGFPlots.Plots.Plot,1}; xlabel=L"$k$", xticks=0:4)).
I suggest adding this as an optional argument to Axis function.

[mirkobunse]

Just use the style argument

Axis(...; style="xtick={0,1,2,3,4}")

and see the other discussions if you need more details: #42 #88 #175

[jywu20]

Thanks for you answer!