Many of the examples provided within documentation are using a single
dash for the command line arguments, but the telegraf executable
explicitly has two dashes.

There are also some inconsistencies with the ordering of the command
line argument examples.  I've ordered them so that the examples will
show: config, config-directory, input-filter, test

closes #1886

closes #1089

closes #934

closes #816

This will basically make the root directory a place for storing the
major telegraf interfaces, which will make telegraf's godoc looks quite
a bit nicer. And make it easier for contributors to lookup the few data
types that they actually care about.

closes #564

- If we detect errors when gathering stat via socket, return those error
  so it canbe appear in Telegraf log
- Improve fcgi client, also upgrade it to current version of Go at
  https://golang.org/src/net/http/fcgi/fcgi.go
- Add test for unix socket and fcgi
  to remotely connect but only as an extra url field.
- Allow customization of fpm status path
- Document about using of `host` in case `unixsocket` that it isn't used
- Documet upgrade for new data layout

closes #499
closes #502
closes #538