Include actual version in runtime path name.

Replace ".../diffpy/libdiffpy13" --> ".../diffpy/libdiffpy-1.3"
Follow prevalent convention for directory naming in prefix/share/.
This closes #3.

src/SConscript

@@ -82,7 +82,7 @@ SConscript('diffpy/SConscript.version')
 
 # Path where datafiles should be installed
 env['runtimepath'] = os.path.join(
-        env['datadir'], 'diffpy/libdiffpy%i%i' % env['majorminor'])
+        env['datadir'], 'diffpy/libdiffpy-%i.%i' % env['majorminor'])
 SConscript('runtime/SConscript')
 
 # Load all other sconscripts that update lib_includes and lib_sources

src/diffpy/runtimepath.cpp

@@ -41,8 +41,9 @@ const char* runtimerelpath =
 #ifdef DIFFPYRUNTIMERELPATH
     STRINGIFY(DIFFPYRUNTIMERELPATH)
 #else
-    "../share/diffpy/libdiffpy"
+    "../share/diffpy/libdiffpy-"
     STRINGIFY(DIFFPY_VERSION_MAJOR)
+    "."
     STRINGIFY(DIFFPY_VERSION_MINOR)
 #endif
 ;