Last-minute docs changes (#1166)

* Specify anonymous limits subject to change
* Drop mention of restricted datasets and add link to policy and usage

Author: krivard

docs/api/api_keys.md

@@ -7,10 +7,11 @@ has_children: true
 # Epidata API Keys
 
 Anyone may access the Epidata API anonymously without providing any personal
-data. Anonymous API access is subject to the following restrictions:
+data. Anonymous API access is subject to the following restrictions; they may
+change as we learn more about their impact:
 
 1. public datasets only
-1. rate-limited to 100 requests per hour
+1. rate-limited to 60 requests per hour
 1. only two parameters may have multiple selections
 
 For example, a query for three signals on one date across all counties can be
@@ -22,7 +23,6 @@ Epidata API. You can request an API key by
 [registering with us](https://forms.gle/hkBr5SfQgxguAfEt7).
 Privileges of registration may include:
 
-1. restricted-access datasets
 1. no rate limit
 1. no limit on multiple selections
 

docs/index.md

@@ -20,8 +20,9 @@ data. Anonymous API access is currently rate-limited and restricted to public
 datasets with a maximum of two of the requested parameters having multiple
 selections (signals, dates, versions, regions, etc).
 
-To request access to restricted datasets, no rate limit, and unlimited multiple
+To request access with no rate limit and unlimited multiple
 selections, you can [request a registered API key](https://forms.gle/hkBr5SfQgxguAfEt7).
+For policy and usage details, consult the [Epidata API keys documentation](api/api_keys.md).
 
 If you regularly or frequently use our system, please consider using an API key
 even if your usage falls within the anonymous usage limits. API key usage helps