Merge pull request #16 from cschreib/update

Refactor tests

Merge pull request #15 from cschreib/update

Update and bug fixes for alignment

Merge pull request #13 from cschreib/observer_constructor

Add casting from owner constructor to basic_observer_ptr

Merge pull request #11 from cschreib/msvc-warning

Fix MSVC warning

Merge pull request #6 from cschreib/policy

Introduce policies and allow `observer_from_this` in constructors

Bump up the action/cache version

Removed unwanted and unneeded check against self assignment

Merge pull request #5 from cschreib/pointer_casts

Add pointer casts

Merge pull request #4 from cschreib/enable_observer_from_this_optim

Bug fixes for enable_observer_from_this

Merge pull request #3 from cschreib/enable_observer_from_this

Add `enable_observer_from_this` and fix self assignment/swap