Add pie chart for used languages

[e-caste]

The result should be a pie chart with e.g. 42% PHP 41.9% PHP, 10% Bash, 3% VHDL, 3.1% JavaScript

[alecello]

Should we add a prompt and relative command line option to ask the user wether they want to generate those stats or do we just generate them whenever we generate SLOC stats?

Also, should we add those statistics to the textual output too?

[e-caste]

@alecello If they can be computed with the SLOC stats (and they should, since cloc provides the means to do so) then do it.
They can’t be generated with the —-no-cloc option, so in that case skip it.

The best output should probably be:

• an additional svg in the output/timestamp/owner directory
• the stats printed to the text output and consequently saved to stats.txt (implement this as you prefer, if it’s possible to add this output to lines_output then it’s fine, if you need another variable to maintain compatibility with no-cloc it works as well)

[alecello]

@e-caste It's possible to implement this independently from cloc with the GitHub API: https://api.github.com/repos/{owner}/{repo}/languages

This way the stats can also be generated with cloc but need a separate set of requests.

[e-caste]

@alecello Then we can:

• if —cloc and -no-lang
  • compute language stats from cloc (if it’s easy, otherwise don’t do it)
• if -lang is given (independently from -cloc)
  • compute language stats from the APIs

Then, let’s add a command line option and corresponding interactive prompt

[e-caste]

Also, I have not specified this, but it makes sense to also have a global statistic with used languages.
I know that GitHub computes used languages for each repo, and the corresponding pie chart could also be added to the repo-specific graphs, but what I am really interested in is the global language usage (so that we can add it to our yearly report).

[e-caste]

Closed with #22