Update contributor docs to reflect San Diego reference implementation

docs/contributing.md

@@ -120,16 +120,14 @@ class Site:
     def scrape_meta(self, throttle=0):
         # 1. Scrape metadata about available files, making sure to download and save file
         #    artifacts such as HTML pages along the way (we recommend using Cache.download)
-        # 2. Generate a metadata CSV and store in the cache
-        # 3. Return the path to the metadata CSV
+        # 2. Generate a metadata JSON file and store in the cache
+        # 3. Return the path to the metadata JSON
         pass
 
-    def scrape(self, metadata_csv):
-        # 1. Use the metadata CSV generated by `scrape_meta` to download available files
-        #    to the cache directory (once again, check out Cache.download).
-        #    artifacts such as HTML "index" pages along the way in the cache
-        # 2. Generate a metadata CSV and store in the cache
-        # 3. Return the path to the metadata CSV
+    def scrape(self, throttle, filter):
+        # 1. Use the metadata JSON generated by `scrape_meta` to download available files
+        #    to the cache/assets directory (once again, check out Cache.download).
+        # 2. Return a list of paths to downloaded files
         pass
 ```
 
@@ -139,7 +137,7 @@ When creating a scraper, there are a few rules of thumb.
     should be saved to the cache unedited. We aim to store pristine
     versions of our source data.
 1.  The metadata about source files should be stored in a single
-    CSV file. Any intermediate files generated during file/data processing should
+    JSON file. Any intermediate files generated during file/data processing should
     not be written to the data folder. Such files should be written to
     the cache directory.
 1.  Files should be cached in a site-specific cache folder using the agency slug name:  `ca_san_diego_pd`.