[Go] 1.4 release runtime note

https://golang.org/doc/go1.4#runtime

• Interface always store pointer into the value part, never store literal type value even if it's size can fit into a pointer size.
• stacks are no longer segmented, When a stack limit is reached, a new, larger stack is allocated, all active frames for the goroutine are copied there, and any pointers into the stack are updated.
  Allocate each Go routine a contiguous piece of memory for its stack, grown by reallocation/copy when it fills up.
  Design doc:
  https://docs.google.com/document/d/1wAaf1rYoM4S4gtnPh0zOlGzWtrZFQ5suE8qr2sD8uWQ/pub
• The use of contiguous stacks means that stacks can start smaller without triggering performance issues, so the default starting size for a goroutine's stack in 1.4 has been reduced from 8192 bytes to 2048 bytes.