Enforce stricter interval algebra rules for overlaps and contains

[KarthikRIyer]

#659
Currently I have just updated the overlaps definition. I'll update contains tomorrow.

[KarthikRIyer]

@meshula I've updated both the definitions. Please take a look.

[meshula]

I think this is a good step for preciseness in implementation. It lgtm, but I'd like to get at least one other reviewer to look at it as well.

[ssteinbach]

Tightening this stuff up is great, and suggests the need for another convenience predicate: intersects -- see the notes in the reviews about that. Thanks for building all of this!

[KarthikRIyer]

@ssteinbach PR updated.

inline constexpr bool greater_than_exclusive(lh, rh, epsilon)
I thought we could drop exclusive here because actually we're just comparing doubles and we could pass in exclusive or inclusive times. Does that make sense?

[ssteinbach]

Fixes #700

[meshula]

Looking good!

[meshula]

Looks like we can't use constexpr without more changes. Why don't we make greater_than and less_than inline for now?

 /tmp/pip-req-build-9j_a1bx9/src/opentime/timeRange.h:28:7: note: ‘opentime::v1_0::TimeRange’ is not literal because:
453   class TimeRange {
454         ^
455  /tmp/pip-req-build-9j_a1bx9/src/opentime/timeRange.h:28:7: note:   ‘opentime::v1_0::TimeRange’ is not an aggregate, does not have a trivial default constructor, and has no constexpr constructor that is not a copy or move constructor
456  /tmp/pip-req-build-9j_a1bx9/src/opentime/timeRange.h:319:27: error: enclosing class of constexpr non-static member function ‘bool opentime::v1_0::TimeRange::lesser_than(double, double, double) const’ is not a literal type
457       inline constexpr bool lesser_than(double lhs, double rhs, double epsilon) const{

[ssteinbach]

This looks great, thanks!