update interface calls in README
add missing imports
ignore vim swapfiles
substitute expired test certificates
fix failing test_signature_string_bad_passphase

also, do pass a passphrase to test_signature_string_verification
so that we have something to compare to.
do not expand shell on subprocess
Merge branch 'master' into develop
Merge remote-tracking branch 'kalikaneko/fix-expired-test-certs' into develop
Merge remote-tracking branch 'kalikaneko/doc-fixes' into develop
Merge remote-tracking branch 'kalikaneko/feature/subprocess_shell_false' into develop
Merge branch 'release/1.3.0'