Trojan v0.8.5

Changelog

• Remove all reregister calling, only register once and read until WouldBlock, then immediately write until done or WouldBlock.
• Using WouldBlock for buffer limitation
• Unify connection status and extract a trait for it
• Move configuration to lazy_static for reducing parameters
• Remove ip marker as it is not necessary
• Optimize connection closing implementation for more readbility