Merge branch 'complex'
Merge remote-tracking branch 'origin/complex'
Merge branch 'master' into matrix
src: added 'base.hpp'
src: inherited 'struct base'
Merge branch 'complex'
Merge branch 'complex' into matrix
Merge remote-tracking branch 'origin/matrix'
src: abstracted classes
src: moved 'Complex.is_scalar()' into base
src: changed modifier of 'base::is_scalar' from public to private
src: added 'Complex_fwd.hpp'
src: added 'Matrix_fwd.hpp'
src: modified some code with 'Complex_fwd.hpp' and 'Matrix_fwd.hpp'
src: added instance method 'Matrix.equals()'
test: added 'Matrix.equals()' testing
readme: added 'Matrix.equals()' api
src: added instance method 'Matrix.isApprox()'
test: added 'Matrix.isApprox()' testing
readme: added 'Matrix.isApprox()' api