correct documentation of some config elements

Closes #1380
Update metrics.rb example

Update the example because output doesn't have the message parameter, instead it should use a a codec.
Also update the way how logstash is executed.
Removed version info in LS command
Closes #1362
Add tilde to UNIXPATH

Tilde '~' is a valid character in UNIXPATHs.

Closes #1195
reject invalid UNIX timestamp
stronger regex and code-style change
fix failing test
use non-capturing group in float regex
Closes #1253
Merge git://github.com/logstash/logstash