Respect cache parameter

Author: mkelley

sbpy/spectroscopy/sources.py

@@ -137,7 +137,7 @@ def from_file(cls, filename, wave_unit=None, flux_unit=None,
 
         # URL cache because synphot.SourceSpectrum.from_file does not
         if _is_url(filename):
-            fn = download_file(filename, cache=True)
+            fn = download_file(filename, cache=cache)
         else:
             fn = filename