FIX #242

FIX #216

because Uniprot has been updated

to enable displaying it as icons in the admin interface

and add unit tests for it

WIP on #68

compounds are visible only if validated or if the user is the creator
or an admin.
WIP on #67

(commit 7143e9d0 on #139)

basically, this adds:
- a CI step to run flake8, _including_ the black plugin to check
  whether or not files need black reformatting
- add flake8 and black to dependencies
- reformat files and correct style so that current code passes

- avoid generating internal server errors if parameter missing or
invalid
- strip input SMILES in case of a bad copy/paste

the format of the returned json has slightly changed, see below, therefore
we are now testing the values returned in the json

before:

```json
{
  'inchi': 'InChI=1/C7H5N3O6/c1-4-6(9(13)14)2-5(8(11)12)3-7(4)10(15)16/h2-3H,1H3',
  'smiles': '[N+](=O)([O-])C1=C(C)C(=CC(=C1)[N+](=O)[O-])[N+](=O)[O-]',
  'stdinchi': 'InChI=1S/C7H5N3O6/c1-4-6(9(13)14)2-5(8(11)12)3-7(4)10(15)16/h2-3H,1H3',
  'stdinchikey': 'SPSSULHKWOKEEL-UHFFFAOYSA-N'
}
```

after:

```json
{
  'inchi': 'InChI=1/C7H5N3O6/c1-4-6(9(13)14)2-5(8(11)12)3-7(4)10(15)16/h2-3H,1H3',
  'smiles': '[N+](=O)([O-])C1=C(C)C(=CC(=C1)[N+](=O)[O-])[N+](=O)[O-]',
  'status': 'SUCCESS',
  'stdinchi': 'InChI=1S/C7H5N3O6/c1-4-6(9(13)14)2-5(8(11)12)3-7(4)10(15)16/h2-3H,1H3',
  'stdinchikey': 'SPSSULHKWOKEEL-UHFFFAOYSA-N'
}
```

this test currently fails (a 500 response), but this is because
the code itself is failing (see #73)