Move all the raw tweets for tests into their own JSON files

Seems better to have the raw data as JSON, like it comes from the API,
then load it into python objects for each test.

tests/tweets/symbols.json

@@ -0,0 +1,61 @@
+{
+  "text":"Some symbols: $AAPL and $PEP and $ANOTHER and $A.",
+  "contributors":null,
+  "geo":null,
+  "favorited":true,
+  "in_reply_to_user_id_str":null,
+  "user":{
+    "screen_name":"philgyfordtest",
+    "name":"Phil Gyford Test"
+  },
+  "in_reply_to_user_id":null,
+  "retweeted":false,
+  "coordinates":null,
+  "place":null,
+  "in_reply_to_status_id":null,
+  "lang":"en",
+  "in_reply_to_status_id_str":null,
+  "truncated":false,
+  "retweet_count":0,
+  "is_quote_status":false,
+  "id":662694880657989632,
+  "id_str":"662694880657989632",
+  "in_reply_to_screen_name":null,
+  "favorite_count":1,
+  "entities":{
+    "hashtags":[
+
+    ],
+    "user_mentions":[
+
+    ],
+    "symbols":[
+      {
+        "indices":[
+          14,
+          19
+        ],
+        "text":"AAPL"
+      },
+      {
+        "indices":[
+          24,
+          28
+        ],
+        "text":"PEP"
+      },
+      {
+        "indices":[
+          46,
+          48
+        ],
+        "text":"A"
+      }
+    ],
+    "urls":[
+
+    ]
+  },
+  "created_at":"Fri Nov 06 18:15:46 +0000 2015",
+  "source":"<a href=\"http://twitter.com\" rel=\"nofollow\">Twitter Web Client</a>"
+}