Update README.md

[asan-emirsaleh]

Correct basal package path and name fixed.
Graphs.jl > LightGraphs.jl

[matbesancon]

thanks for the PR, I'm not sure this is necessary given that LGExtras is more or less inactive (doesn't even have a Project.toml)

[matbesancon]

thoughts @gdalle @simonschoelly ?

[gdalle]

Yes, I recommend you use (and possibly contribute to) the new package GraphsExtras.jl instead of this older one

[asan-emirsaleh]

Thank you. Ok.
But as I understood the LightGraphsExtras.jl is addition to LightGraphs.jl, not to Graphs.jl. Also there is a reference to LightGraphsExtras.jl in LightGraphs's page. So I decided to fix this inconsistency.

[asan-emirsaleh]

I checked the concordance of this page's description, doc page and Readme.
Description: Additional functionality for LightGraphs.jl
doc page of LightGraphs.jl: [LightGraphsExtras.jl](https://github.com/JuliaGraphs/LightGraphsExtras.jl): extra functions for graph analysis
README: Extra functionality for [Graphs](https://github.com/JuliaGraphs/Graphs.jl).

The link to the doc in README is invalid:
Documentation for this module is available at [Read The Docs](http://lightgraphsextrasjl.readthedocs.io/en/latest/?badge=latest)

So I suggest:

1. fix the link to the LightGraphs.jl
2. add the notion about the LightGraphsExtras.jl be discontinued
3. fix the doc page linked from the README

[gdalle]

Sorry for the delay @asan-emirsaleh. I'm okay with the changes you propose, if you want to flesh out your PR I'll review it