Setting default IDLE notify interval to 29 mins

This is per [RFC 2977](http://tools.ietf.org/html/rfc2177)
Setting default max user IP connections to 3

This is per @mjhas's comments on PR #9

I could not locate any certain default setting for this, besides the "default" of 10 in `/usr/share/dovecot/conf.d/20-imap.conf`; however, it appears to be more of an example than a default value.