Only rerun fails that are marked
Update README.md
Changed marker to 'flaky'
Update README.md
Add flaky marker, add keyword max_runs to marker

Can now mark tests with @pytest.mark.flaky(max_runs=3) to run a test up to 3 times. 
No longer need to specify reruns at command line. 
Do not need to include flaky marker in pytest.ini
Renamed max_runs to reruns
Update README.md
Added a couple of tests to check flaky marker

test_flaky_test_with_1x_marker and test_flaky_test_with_1x_marker
Changed global vs marker logic to prefer marker, but still respect global setting
Fixed checking for wrong keyword.
Updated usage.
Added flaky marker test case
Reorganized the code a bit
Update README.md
Merge pull request #15 from fireflash38/master

Add flaky marker allowing you to mark specific tests to rerun rather than all tests