Update Flake8 config

Exclude import warnings from tests

Restore Flake8 docstring convention to numpy style

Author: bosd

.flake8

@@ -3,7 +3,7 @@ select = B,B9,C,D,DAR,E,F,N,RST,S,W
 ignore = E203,E501,RST201,RST203,RST301,W503
 max-line-length = 120
 max-complexity = 10
-docstring-convention = google
-per-file-ignores = tests/*:S101
+docstring-convention = numpy
+per-file-ignores = tests/*:S101,S106,F403,F405,F841
 rst-roles = class,const,func,meth,mod,ref
 rst-directives = deprecated