Add gRPC release schedule document

[srini100]

Not including actual release dates for ease of maintenance. Will be linking to this doc from other repos and grpcio FAQ.

[hsaliak]

a few minor nits..

[jtattermusch]

nit: should this document rather live in grpc.io repository?

[srini100]

I think this directory gets more eyes from users. We will link to this from the FAQ section in grpc.io.

[jtattermusch]

nit: it may be good to interesting to mention the motivation behind six-weekly release schedule (e.g. good balance of delivering new features and fixes quickly to the users and not having too much release overhead, and explaing why we chose fixed release schedule over variable one)

[srini100]

Done. Don't want to make it too verbose so skipped the rationale for fixed vs. variable release.

[grpc-testing]

Objective-C binary sizes
*****************STATIC******************
  New size                      Old size
 2,020,224      Total (=)      2,020,224

 No significant differences in binary sizes

***************FRAMEWORKS****************
  New size                      Old size
11,154,229      Total (<)     11,154,231

 No significant differences in binary sizes

[grpc-testing]

Objective-C binary sizes
*****************STATIC******************
  New size                      Old size
 2,020,224      Total (=)      2,020,224

 No significant differences in binary sizes

***************FRAMEWORKS****************
  New size                      Old size
11,154,225      Total (>)     11,154,223

 No significant differences in binary sizes

[grpc-testing]

Objective-C binary sizes
*****************STATIC******************
  New size                      Old size
 2,020,224      Total (=)      2,020,224

 No significant differences in binary sizes

***************FRAMEWORKS****************
  New size                      Old size
11,154,235      Total (>)     11,154,228

 No significant differences in binary sizes

[grpc-testing]

****************************************************************

libgrpc.so

     VM SIZE        FILE SIZE
 ++++++++++++++  ++++++++++++++

  [ = ]       0        0  [ = ]


****************************************************************

libgrpc++.so

     VM SIZE        FILE SIZE
 ++++++++++++++  ++++++++++++++

  [ = ]       0        0  [ = ]

[grpc-testing]

[trickle] No significant performance differences

[grpc-testing]

Objective-C binary sizes
*****************STATIC******************
  New size                      Old size
 2,020,300      Total (=)      2,020,300

 No significant differences in binary sizes

***************FRAMEWORKS****************
  New size                      Old size
11,154,431      Total (<)     11,154,434

 No significant differences in binary sizes

[grpc-testing]

Corrupt JSON data (indicates timeout or crash): 
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.new: 10
    bm_call_create.BM_IsolatedFilter_ClientChannelFilter_NoOp_.counters.old: 10


[microbenchmarks] No significant performance differences

[srini100]

@jtattermusch, any other suggestions?