[Suggestion] Substitute the parameterized type with (<>)

[guo jiwei]

Hi dev,
   TubeMQ compiles with Java 1.7 or above, so I suggest to remove the
parameterized type, and substitute with (<>) instead.
   example: List<String> list = new ArrayList<String>(); -> List<String>
list = new ArrayList<>();
   If we think we should do it, Viviel(contributor) and I will split the
task (for it involves almost all the classes) to make it.