release version 0.5.2

Merge pull request cta-observatory#463 from kosack/master

more cleanups for instrument class usage

Merge pull request cta-observatory#437 from kosack/improve_examples

Improve examples

Merge pull request cta-observatory#345 from kosack/master

update history for release

Merge pull request cta-observatory#323 from kosack/master

more fixes for version.py

Merge pull request cta-observatory#316 from kosack/master

fix build system so packages can be made

Merge pull request cta-observatory#303 from kosack/master

remove pytest-runner which has no conda package

Merge pull request cta-observatory#301 from kosack/master

Fix tests for Factory and Tool

Merge pull request cta-observatory#283 from watsonjj/filereader

EventFileReader

Merge pull request cta-observatory#276 from kosack/master

fix readme formatting