Add examples to README

This fixes #3.

README.markdown

@@ -8,9 +8,53 @@ The toolset
 ### histogram.py
 Generates an ASCII histogram based on row frequency.
 
+Example:
+
+```bash
+$ cat > tmpfile                                                                                                                                          [21:24:30]
+a
+b
+a
+a
+c
+$ cat tmpfile| python histogram.py                                                                                                                     [21:24:57]
+a: ################################################################################ (3)
+b: ########################## (1)
+c: ########################## (1)
+```
+
 ### cache_simulator.py
 Used to simulate how a cache could improve performance given a list of
-`<timestamp, requests>` pairs from a text file.
+`<timestamp, requests>` pairs from a text file. The cached key-values are
+expired TTL seconds after last usage.
+
+Usage:
+
+```bash
+python cache_simulator.py --help                                                                                                                     [21:54:46]
+usage: cache_simulator.py [-h] [-t TTL] [-s SEPARATOR] [-d DATEFORMAT]
+                          [inputfiles [inputfiles ...]]
+
+A simple cache simulator.
+
+positional arguments:
+  inputfiles            An input file consisting of one event per line. Each
+                        line starts with a date, followed by a separator and a
+                        cache key. If no input file is specified stdin is
+                        expected.
+
+optional arguments:
+  -h, --help            show this help message and exit
+  -t TTL, --ttl TTL     Time to live before a cached value is expired (in
+                        seconds). Default is 60.
+  -s SEPARATOR, --separator SEPARATOR
+                        The separator to use between the date and the key.
+                        Defaults to 'None'.
+  -d DATEFORMAT, --dateformat DATEFORMAT
+                        Date format (default=%Y-%m-%d). See
+                        http://docs.python.org/library/datetime.html for
+                        information about the date format markup language.
+```
 
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