Initial Proposal for QuickVega

[davibarreira]

This is a very substantial amount of code. Here is an overview of what is coded:

• lineplot, barplot, histogram (1d), scatterplot, contourplot.
  Each one has multiple dispatch, enabling the user to pass the actual vectors, or dataframes, or matrices.
  The code for each plot is straightforward.

The other main part of the code is the file updateSpec.jl. In this file, there is the function updatePlot!, which receives a VLSpec
and modifies according to the argument supplied. This function is responsible for modifying the plots accordingly to the kwargs
sent by the users in the original plots. The function is just a long list of conditionals, where each conditional identifies
the argument sent by the user and modifies the plot.

I've also implemented a way for the user to set default settings for all plots, which can be done by modifying the QuickVega.defaultParameters dictionary. Also, I've created a "dark theme", which can be used by calling the function
setTheme!(:dark).

Inside the folder "sandbox" there is a jupyter notebook file with examples for all the code implemented.

Oh, I've also created a logo, listed some possible "desirable features" and put all in the Readme.