Default closest_limit to 100 instead of 10 (#606)

At UKWA we're hitting cases where crawl variation means we have e.g. a lot of redirect records and in these cases the 10 record limit is too low.  I can't see any way of configuring this value, so I'm proposing the default is raised.

pywb/warcserver/index/indexsource.py

@@ -113,7 +113,7 @@ def init_from_config(cls, config):
 class RemoteIndexSource(BaseIndexSource):
     CDX_MATCH_RX = re.compile('^cdxj?\+(?P<url>https?\:.*)')
 
-    def __init__(self, api_url, replay_url, url_field='load_url', closest_limit=10):
+    def __init__(self, api_url, replay_url, url_field='load_url', closest_limit=100):
         self.api_url = api_url
         self.replay_url = replay_url
         self.url_field = url_field