Fix typos
graphite api: add support for sending metrics over UDP

There already exists an API for sending metrics to InfluxDB over TCP using
Graphite plaintext protocol. Sometimes it is more convenient to send metrics
over UDP, so adding that support for the Graphite as well. For now at least,
using the same port for UDP traffic than for TCP to make configuration really
simple.

UDP listener is disabled by default, but can be turned on by setting udp_enabled
to true in graphite plugin configuration.
Merge pull request #546 from peekeri/graphite_udp_api

graphite api: add support for sending metrics over UDP
Merge pull request #545 from freeformz/typo

Fix typos
Update CHANGELOG.md
Update CHANGELOG.md
Close #551. Fix #409. Add aggregate funciton top and low

this patch provides aggregate function top and low. these function are
useful when executing analytics or summarize queries.

Added functions:
  low(columns..., limit)
  top(columns..., limit)

For instance:
  `select low(value, 10) from series` will output 10 `value` values with ascending order.
  `select top(value, 10) from series` will output 10 `value` values with descending order.

How to build:
  go get github.com/ryszard/goskiplist/skiplist
  go build src/daemon.go

Currently, these function support float64 and int64 types.

Limitations:
  * can't handle same value correctly (goskiplist limitation)

Misc:
  * each column should support alias.
    e.g) low(score as low_score, 10)

And, I'm not good at English and Golang. so if you find some wrong
points, plz feel free to fix it.
modify some tests
more idiomatic go
Merge branch 'pr-551'
update the changelog
fix a log statement
add some logging
Fix #555. Fix a regression in d593348 where the snapshot format changed
remove newlines from log statements
update the changelog
Fix #557. Using group by time(1y) doesn't work while time(365d) is fine
Fix #460. Don't start influxdb automatically after installing from pkg
Fix #529. Don't run influxdb as root
fix the style of the changelog