update README.md with some missing documentation/notes

README.md

@@ -534,7 +534,7 @@ technically still exists under previous version numbers).
 ### Authentication
 
 If you need to access FHIR resources on a server requiring authentication, you can
-wrap all of your FHIR calls in `with-auth` which takes a parameter that can specify
+wrap all of your FHIR calls in `with-options` which takes a parameter that can specify
 HTTP [basic authentication](http://en.wikipedia.org/wiki/Basic_access_authentication), 
 [digest authentication](http://en.wikipedia.org/wiki/Digest_access_authentication) 
 or an [OAuth bearer token](http://self-issued.info/docs/draft-ietf-oauth-v2-bearer.html).
@@ -550,18 +550,45 @@ strings (username and password) or a single string containing both separated by
 (search server-url :patient [(eq :name "smith")])
 
 ; HTTP basic auth
-(with-auth {:basic-auth ["user" "pass"]}
+(with-options {:basic-auth ["user" "pass"]}
   (search server-url :patient [(eq :name "smith")]))
 
 ; HTTP digest auth
-(with-auth {:digest-auth ["user" "pass"]}
+(with-options {:digest-auth ["user" "pass"]}
   (search server-url :patient [(eq :name "smith")]))
 
 ; OAuth bearer token
-(with-auth {:oauth-token user-oauth-token}
+(with-options {:oauth-token user-oauth-token}
   (search server-url :patient [(eq :name "smith")]))
 ```
 
+### Adding Custom HTTP Headers to FHIR Requests
+
+If the FHIR server you're making requests to needs some additional HTTP headers for
+any reason, you can again use `with-options` to add these.
+
+##### Example
+
+```clojure
+; all FHIR requests within the with-options body will have the specified
+; HTTP headers included
+(with-options {:headers {"FOO" "bar"}}
+  (get-resource server-url :patient 42))
+```
+
+### Self-Signed SSL Certificates
+
+If you need to make request to a FHIR server over HTTPS but it is using a self-signed
+SSL certificate you will again need to use `with-options` and provide the `:insecure?`
+setting.
+
+##### Example
+
+```clojure
+(with-options {:insecure? true}
+  (get-resource server-url :patient 42))
+```
+
 ### Error Handling
 
 All API functions throw exceptions via `ex-info` when an unexpected error response is
@@ -569,6 +596,10 @@ returned from the HL7 FHIR server. An "unexpected error response" is anything th
 is not defined to be part of the particular operation's successful result(s). e.g.
 a "read" operation that returns an HTTP 400 or HTTP 500 status instead of HTTP 200.
 
+> **NOTE:** Some servers differ in how they return errors (e.g. different HTTP status
+> codes), so you will want to be sure to test your code's error handling to be sure 
+> errors are caught correctly!
+
 When this type of response is encountered, an exception is thrown which will contain
 the response, which can be obtained in your exception handler via `ex-data`. If the
 response is detected to be a FHIR [OperationOutcome](http://www.hl7.org/implement/standards/fhir/operationoutcome.html)