Fix the 'happiness' bug

Fixes #258

This commit fixes the issue of the "empty Ngrams". The culprit was a bug
in the `arxiv-api` package, which was fixed by:

gargantext/crawlers/arxiv-api!2 (commits)

In a nutshell, due to the fact the relevant `Conduit` was never
completing, it was blocking the `flow` function, which was endlessly
waiting for the last part of the results to arrive.

Hence we were never calling the `flowCorpusUser`, which is the function
responsible for generating the Ngrams.
3 jobs for adinapoli/issue-258-part-2 in 9 minutes and 51 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Stack
passed #8334
stack

00:00:43

 
  Cabal
passed #8335
cabal

00:07:59

 
  Test
failed #8336
test

00:01:08

 
Name Stage Failure
failed
test Test
Config file path source is default config file.
Config file not found: /root/.config/cabal/config
Writing default configuration to /root/.config/cabal/config
fatal: unsafe repository ('/builds/gargantext/haskell-gargantext/dist-newstyle/src/arxiv-api-f5d5ddb2088f38ab' is owned by someone else)
To add an exception for this directory, call:

git config --global --add safe.directory /builds/gargantext/haskell-gargantext/dist-newstyle/src/arxiv-api-f5d5ddb2088f38ab
Cleaning up file based variables
ERROR: Job failed: exit code 1