Create timeout plugin

This plugin manage timeout. Default timeout is 60 seconds.
If happen timeout, decanter return the http status code 503.

You can override that time by app/config/settings.py .
settings.py:
`timeout = 30`

Furthermore, you can override each function of controller by decorator.
@get('/home/<name>', timeout=30)
Merge pull request #83 from narusemotoki/timeput_plugin

Create timeout plugin