Roll src/tools/swarming_client/ to 77f720b047fe45f42223e1117b18a8a0a2e38052.

Roll src/tools/swarming_client/ to 77f720b047fe45f42223e1117b18a8a0a2e38052.

$ git log 49f046853..77f720b04 --date=short --format='%ad %ae %s'
2015-09-15 maruel Reapply "Isolated task support in Endpoints API: client side (3/3)" and fixes"
2015-09-15 maruel Significant refactoring of run_isolated.
2015-09-14 maruel Minor fixes to fix isolated tasks.
2015-09-11 maruel Improve cost.py and add fleet.py.
2015-09-10 maruel Revert "Isolated task support in Endpoints API: client side (3/3)" and fixes"
2015-09-10 maruel Fix second regression in be9d81eb7fb34b.
2015-09-10 maruel Add client/tools/cost.py to calculate stats on swarming tasks.
2015-09-10 maruel Fix regression in be9d81eb7fb34b2137.
2015-09-10 maruel Reapply "Isolated task support in Endpoints API: client side (3/3)" and fixes"
2015-09-09 maruel Fix log file rotation on Windows w/ child process and add regression test.
2015-09-09 maruel Make all swarming bot subprocesses detached.
2015-09-08 maruel Improve handling of autoscaler shutting down a VM in the middle of a task
2015-09-05 maruel Enforce that the bot code in memcache is valid.
2015-09-04 maruel Enable running Swarming local smoke test on Windows.

R=vadimsh@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1344123002

Cr-Commit-Position: refs/heads/master@{#349044}