stbt lint: Print usage if no arguments given
stbt lint: Print usage if no arguments given

This is a slightly nicer experience than seeing the pylint help output,
which tells you to run pylint.

LewisHaley/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester