=== Science ===
The directory Science/ now contains files corresponding to
the various functions in the now-removed Science.cpp.

Filenames correspond directly with the function name, and each
file contains only one functions, with a few notable exceptions.
 - Science/get_quads.cpp contains get_quads_x, get_quads_y, and get_quads_z
 - Science/compute_background_PE contains the helper function
compare_pairs

The global variables _quadw_x, _quadw_y, and _quadw_z are declared as
extern in Science.hpp and declared in Science/compute_quadweights.cpp

=== Makefile ===
The Makefile has been modified accordingly. It now automatically detects
all Science/*.cpp files and includes them in the compile recipe.

The Makefile has also been tidied up a little bit by defining a variable
SPINS_BASE which points to the core files.