Fix typos discovered by codespell

[cclauss]

Fix typos discovered by codespell - https://pypi.org/project/codespell

% codespell

./README.md:28: overriden ==> overridden
./scheduler/decorators.py:44: Arbitraty ==> Arbitrary
./scheduler/templates/admin/scheduler/job_detail.html:86: interation ==> iteration, interaction, integration
./scheduler/worker/worker.py:287: bootstraping ==> bootstrapping
./scheduler/worker/worker.py:566: Get's ==> Gets
./scheduler/helpers/timeouts.py:46: supress ==> suppress
./docs/configuration.md:17: overriden ==> overridden
./docs/installation.md:63: overriden ==> overridden

% codespell --write-changes

@cunla @carltongibson @matthiask