Philip Hyunsu Cho 9975c533c7
Re-organize contributor's guide (#4659)
* Reorganize contributor's doc

* Address comments from @trivialfis

* Address @sriramch's comment: include ABI compatibility guarantee

* Address @rongou's comment

* Postpone ABI compatibility guarantee for now
2019-07-15 20:56:05 -07:00
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