Repository: diofant/diofant

Issue:
Project logo
There are few places to put images:
- [x] Top left corner of https://diofant.readthedocs.io/ (see e.g. https://sphinx-rtd-theme.readthedocs.io/)
- [x] favicon.ico.
- [x] logo for pdf logs
- [x] Organization profile on the Github (at least 200x200px)
- [x] ~~repository’s social media preview (640×320px - 1280×640px for best display)~~



Discussion:
@skirpichev   Hi, my name is Richard. I'm a graphic designer and I love making contributions for open source projects. I see that they want a new logo for your application. If you wish, I can do it for you without any problem ... I can present some modern ideas that would improve the appearance and image of your project
> I can present some modern ideas that would improve the appearance and image of your project

Any help would be appreciated.  But keep in mind - there is currently no images to improve, apparently this was not clear from beginning...

There are few places, where such images could be placed.  First, as a project homepage we use https://diofant.readthedocs.io/, where the docs live.  It uses [sphinx-rtd-theme](https://sphinx-rtd-theme.readthedocs.io/en/latest/index.html) sphinx theme, which support logo at the top left corner of the page, [see example](https://docs.readthedocs.io/en/stable/).  Favicon could be specified too.  And there is the [profile on github](https://github.com/diofant), which has place for organization's avatar.


@skirpichev  perfect I can do all that for you. can you tell me what the project is about and so be able to do something that is consistent with it
You can take look on the referenced homepage.
@skirpichev  I present this proposal that is inspired to represent a snake to relate to Python, but at the same time is made to express the letter D which is the initial name of your project so it becomes a unique and personal image that can be easily remember to find the project. I hope you like it, if you want some change you can only ask for it and I will gladly do it, if you want to use it without any modification I can create a google folder with all the necessary files to use the logo.

![logo1252](https://user-images.githubusercontent.com/35604837/52060505-b8341100-2542-11e9-9b1f-e056fda5534d.png)


![logo125horizontal](https://user-images.githubusercontent.com/35604837/52060864-87081080-2543-11e9-8fb9-df77cd552ca8.png)

Not bad, as a variant, but I'm not sure if yellow-based coloring scheme will fit our sphinx theme.  See current [docs](https://diofant.readthedocs.io/en/latest/).

But if you could try other variants - please do.  This project more about computer algebra then about the Python language (which is more or less an accident of the current implementation).  Maybe some reference to the original symbolic notation of Diophantus could enter the logo.  For inspiration you may take look on this sample:
![image](https://user-images.githubusercontent.com/2155800/52073891-a92c7d80-2599-11e9-98ac-0fa8624ca4fd.png)
On top of that sample - equation `8*x**3 - 16*x**2 = x**3`.  Square of the unknown variable (ς) he denoted as
```
 γ
Δ 
```
For cube:
```
 γ
Κ 
```
He doesn't mention addition, but before subtracted terms adds inverted Ψ letter.


> I can create a google folder with all the necessary files to use the logo.

In general, all work on the project should be submitted via pull requests.  But in this case, you can just attach images to this issue.

Resolving patch:
diff --git a/docs/conf.py b/docs/conf.py
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -119,6 +119,11 @@
 # Should we show "Created using Sphinx" in the HTML footer?
 html_show_sphinx = False
 
+# Paths to the logo and favicon.ico, relative to the conf.py's directory.
+html_logo = '_static/logo.svg'
+html_favicon = '_static/favicon.ico'
+latex_logo = '_static/logo.png'
+
 # Theme-specific options.
 html_theme_options = {
     'logo_only': True,


Test patch: