fix(client): use sys.stdout.write for logs

The logs already print out newline characters, so using print()
adds an extra empty line to the log output. Using sys.stdout.write()
removes this empty line.
fix(logger): remove Source and Tag from output

An application's logs should not contain which host it was listed
on. It should only care about the data that is relevant to it.

The Tag field is unused, so this added an extra whitespace to the
log format. Removing it cleans up the logs a bit.
test(logger): add filehandler tests
test(logger): add log message tests
feat(logger): add make test/coverage
test(logger): hook up logger tests to TravisCI
style(gitignore): add coverage.out to gitignore
test(logger): add priority tests
fix(travis): install go cover
Merge pull request #1132 from deis/log-formatting

test(logger): add syslog tests