Update README.md

Note c1.medium performance.
* filter out undesirable characters
* add testing for auth & php - make sure mod_statsd behaves as expected
* php files
* this is 1.0.1
* support apache notes as a way of setting the stat key
* add header support, document headers & note ways of setting up the statname
* add aggregate support
* support legacy namespace directive
* update changelog
Merge pull request #3 from jib/graphite-legacy-mode

Graphite legacy mode
* this is 1.0.2
Create LICENSE
* use the last status in the response code, not the first. This captures errors from modphp & co
* use the last status in the response code, not the first. This captures errors from modphp & co
* this is 1.0.3
Merge branch 'master' of github.com:jib/mod_statsd