* Down-integrate internal changes to github.

* fix csharp conformance test

* add comments in conformance.proto for text format

* fix comments

* fix comments, re-generated csharp file

* fix comments, re-generated csharp file

* Down-integrate internal changes to github.

* fix python conformance test

* fix csharp conformance test

* add back java map_lite_test.proto's optimize for option

* fix php conformance test

* Remove/replace travis references.

We need to use a default of 0 when parsing unspecified map keys, instead
of failing an assertion.

This change was written by Michael Aaron (michaelaaron@google.com) but I
am cherry-picking it directly instead of waiting for the next sync of
Google-internal changes.

* Fix setup.py for windows build.

* Bump version number to 3.5.2

* Cat the test-suite.log on errors for presubits

This reverts commit f00e06c9.

Although Node Buffers are not covered by the tests, it seems that there
are users relying on them, so we need to add back in support for them.

This fixes issue #4359.

This reverts commit 2bd55a9f.

* Fix js conformance tests.

* Remove old incorrect compatibility tests

Add some supporting documentation regarding Closure for those unfamiliar., Also substantiate details for "files in this directory" - including them all will result in a project that does not compile as some are used for test cases and aren't part of the core library.