aarect.h lacks override keyword on some methods

[trevordblack]

In file included from /home/lucifer/writing/raytracing.github.io/src/TheRestOfYourLife/main.cc:14:
/home/lucifer/writing/raytracing.github.io/src/TheRestOfYourLife/aarect.h:58:24: warning: 'pdf_value' overrides a member function but is not marked 'override' [-Winconsistent-missing-override]
        virtual double pdf_value(const point3& origin, const vec3& v) const {
                       ^
/home/lucifer/writing/raytracing.github.io/src/TheRestOfYourLife/hittable.h:50:24: note: overridden virtual function is here
        virtual double pdf_value(const vec3& o, const vec3& v) const {
                       ^
In file included from /home/lucifer/writing/raytracing.github.io/src/TheRestOfYourLife/main.cc:14:
/home/lucifer/writing/raytracing.github.io/src/TheRestOfYourLife/aarect.h:70:22: warning: 'random' overrides a member function but is not marked 'override' [-Winconsistent-missing-override]
        virtual vec3 random(const point3& origin) const {
                     ^
/home/lucifer/writing/raytracing.github.io/src/TheRestOfYourLife/hittable.h:54:22: note: overridden virtual function is here
        virtual vec3 random(const vec3& o) const {