add supported formatting options to readme

README.md

@@ -53,6 +53,54 @@ There is a at least one key/value in the returned dictionary for each apache log
 
 The version numbers follow [Semantic Versioning](http://semver.org/).
 
+
+Supported values
+========
+```python
+    '%a'  #	Remote IP-address
+    '%A'  #	Local IP-address
+    '%B'  #	Size of response in bytes, excluding HTTP headers.
+    '%b'  #	Size of response in bytes, excluding HTTP headers. In CLF format, i.e. a '-' rather than a 0 when no bytes are sent.
+    '%D'  #	The time taken to serve the request, in microseconds.
+    '%f'  #	Filename
+    '%h'  #	Remote host
+    '%H'  #	The request protocol
+    '%k'  #	Number of keepalive requests handled on this connection. Interesting if KeepAlive is being used, so that, for example, a '1' means the first keepalive request after the initial one, '2' the second, etc...; otherwise this is always 0 (indicating the initial request). Available in versions 2.2.11 and later.
+    '%l'  #	Remote logname (from identd, if supplied). This will return a dash unless mod_ident is present and IdentityCheck is set On.
+    '%m'  #	The request method
+    '%p'  #	The canonical port of the server serving the request
+    '%P'  #	The process ID of the child that serviced the request.
+    '%q'  #	The query string (prepended with a ? if a query string exists, otherwise an empty string)
+    '%r'  #	First line of request
+    '%R'  #	The handler generating the response (if any).
+    '%s'  #	Status. For requests that got internally redirected, this is the status of the *original* request --- %>s for the last.
+    '%t'  #	Time the request was received (standard english format)
+    '%T'  #	The time taken to serve the request, in seconds.
+    '%u'  #	Remote user (from auth; may be bogus if return status (%s) is 401)
+    '%U'  #	The URL path requested, not including any query string.
+    '%v'  #	The canonical ServerName of the server serving the request.
+    '%V'  #	The server name according to the UseCanonicalName setting.
+    '%X'  #	Connection status when response is completed:
+              # X =	connection aborted before the response completed.
+              # + =	connection may be kept alive after the response is sent.
+              # - =	connection will be closed after the response is sent.
+              # (This directive was %c in late versions of Apache 1.3, but this conflicted with the historical ssl %{var}c syntax.)
+    '%I'  #	Bytes received, including request and headers, cannot be zero. You need to enable mod_logio to use this.
+    '%O'  #	Bytes sent, including headers, cannot be zero. You need to enable mod_logio to use this.
+
+    '%\{User-Agent\}i'  # Special case of below, for matching just user agent
+    '%\{[^\}]+?\}i'  #	The contents of Foobar: header line(s) in the request sent to the server. Changes made by other modules (e.g. mod_headers) affect this. If you're interested in what the request header was prior to when most modules would have modified it, use mod_setenvif to copy the header into an internal environment variable and log that value with the %\{VARNAME}e described above.
+
+    '%\{[^\}]+?\}C'  #	The contents of cookie Foobar in the request sent to the server. Only version 0 cookies are fully supported.
+    '%\{[^\}]+?\}e'  #	The contents of the environment variable FOOBAR
+    '%\{[^\}]+?\}n'  #	The contents of note Foobar from another module.
+    '%\{[^\}]+?\}o'  #	The contents of Foobar: header line(s) in the reply.
+    '%\{[^\}]+?\}p'  #	The canonical port of the server serving the request or the server's actual port or the client's actual port. Valid formats are canonical, local, or remote.
+    '%\{[^\}]+?\}P'  #	The process ID or thread id of the child that serviced the request. Valid formats are pid, tid, and hextid. hextid requires APR 1.2.0 or higher.
+    '%\{[^\}]+?\}t'  #	The time, in the form given by format, which should be in strftime(3) format. (potentially localized)
+    '%\{[^\}]+?\}x'  # Extension value, e.g. mod_ssl protocol and cipher
+```
+
 Copyright
 =========