Add some tests for l1 norm

[nperraud]

Just added some tests for check related to issue #19

[nperraud]

@mdeff why is travis not checking this?

[mdeff]

I fixed the CI. Linting however fails. Please fix the following:

./pyunlocbox/tests/test_functions.py:163:1: W293 blank line contains whitespace
./pyunlocbox/tests/test_functions.py:168:36: E231 missing whitespace after ','
./pyunlocbox/tests/test_functions.py:172:53: W291 trailing whitespace
./pyunlocbox/tests/test_functions.py:173:1: W293 blank line contains whitespace
./pyunlocbox/tests/test_functions.py:175:47: E231 missing whitespace after ','
./pyunlocbox/tests/test_functions.py:178:53: W291 trailing whitespace
./pyunlocbox/tests/test_functions.py:179:1: W293 blank line contains whitespace
./pyunlocbox/tests/test_functions.py:181:40: E251 unexpected spaces around keyword / parameter equals
./pyunlocbox/tests/test_functions.py:181:48: E231 missing whitespace after ','
./pyunlocbox/tests/test_functions.py:184:52: W291 trailing whitespace
./pyunlocbox/tests/test_functions.py:185:5: E301 expected 1 blank line, found 0
./pyunlocbox/tests/test_operators.py:407:46: E261 at least two spaces before inline comment
./pyunlocbox/tests/test_operators.py:408:1: W293 blank line contains whitespace
./pyunlocbox/tests/test_operators.py:409:1: W293 blank line contains whitespace
./pyunlocbox/tests/test_operators.py:412:1: E303 too many blank lines (4)

Tip: run make lint locally to check for style issues.

[mdeff]

test_adjoint is a test to check #15

[coveralls]

Coverage increased (+0.03%) to 98.592% when pulling 8accd0c on add-test into d0bd39b on master.

[mdeff]

Thanks for the PR!