[simulator][machine] Simulator config, command and improve logic

[at15]

• logging library. Logrus 7ecdba3
• config simulator using yaml and command line. (might use viper) (we only consider machine for now)
  • machine numbers
  • start, end, interval
• change logic for how simulator generate data, currently, when machine is added to the simulator, it's just their series been added, the MachineSimulator does not know about machine, as suggested by @czheo in [WIP] Data generation #9 the simulator should be aware of machine. I am not very clear how I should change the logic but the output (which is the input for serializer) should be the same, since we are still using the simplest and most verbose format, one series + one data point instead of one series + multiple data points when generating data. When loading the data, it really depends on how the database provide interface for bulk loading, batches can be done in loader, so this should not be the concern for simulator, using database independent format can allow generated be used on multiple databases, which is useful if the data generation is resource consuming.
• write to file
• deserialize file (the part is more used in loader, but it should also be used in serializer's test) leave it it to loader

There are a lot more that could be configured for the machine, like we can add higher level things like rack, data center, for micro benchmark, they are just tags, for real bechmark, those information can be used for deploy probes to machines in different rack, dc. However, they are just too much for now.

[at15]

An example snippet of machine simulator config

simulator:
    machine:
        num: 100
        # start time in ISO 8601
        start: 1997-07-16T19:20:30.45+01:00
        # end time in ISO 8601x
        end: 1997-07-16T19:20:31.45+01:00
        # in second
        step: 10

• use viper to get proper time object 24e067d
• generate simulator from config

[at15]

The plan for refactor the generator logic is like the following

• *rename generator package to distribution
• remove ConstantIntGenerator since it contains both time and value, which is an unnecessary abstraction a908a4a
• remove the SeriesWithGenerator since int generator is removed a908a4a
• add time and value package with FixedInterval and FixedValue to replace the old constant int generator

And the machine simulator logic used to be

• AddMachine
• AddSeriesWithGenerator
• Loop and generate value by Series

Now it will be

• AddMachine
• Loop machine and generate a group of series, the group:
  • share one time stamp from FixedInterval
  • generate different value from FixedValue

[at15]

The plan for the simulator command is like the following

• create simulator config based on command line arguments (may support config in the future)
• create machine simulator config based on simulator config
• create machine simulator based on machine simulator config
• start the simulator
• clean up

some changes need to be made

• add \n for the json serializer (or maybe add it to the writer? I prefer to put it in the serializer)
• support output to file

[at15]

now a small problem for json ouput, it has an extra empty line

{"v":1,"t":869077270450000000,"name":"machine","tag":{"cpu_core":"3","host":"default-2","os":"ubuntu16.04"}}
{"v":1,"t":869077270450000000,"name":"machine","tag":{"cpu_core":"3","host":"default-2","os":"ubuntu16.04"}}

I think the reader could have check when deserialize the data, so I will just ignore it. PTAL @czheo I will merge it tomorrow if no response from u.

[at15]

merge without review. 没时间了，快上车