* Add link to continuous test badges

* Add badge for dist_install

* Remove ruby21 and ruby22 tests

* Update test badge

Add build status badge for Dart

Moved the badges to the language table as they are per-language based.
Some badges are not yet available due to stuck kokoro jobs.

The example utilizes native bazel rules (proto_library, cc_proto_library,
java_proto_library, java_lite_proto_library) to show how easy it is to
build protobuf with bazel's native support. It also makes use of well
known types which was not possible until the latest bazel 0.5.4 release
and https://github.com/google/protobuf/pull/3594 .

Howdy!

I just updated some links to use https instead of http.

Thanks! ^ _ ^

Dedent URL so it renders as a link and not as code (fixed width font and not clickable).

This pull request includes two implementation: C extension and PHP
package. Both implementations support encode/decode of singular,
repeated and map fields.

[ci skip]

Change-Id: I5bf4f204e7ef0144d8fc984a985d502f92ce95ce

[ci skip]

Change-Id: I5bf4f204e7ef0144d8fc984a985d502f92ce95ce

Move the original README.md to src since it's talking about C++
exclusively and add a more general README.md to document how
to install protoc for all languages.

Added instructions on what tools to install to compile protobuf from
source. Removed the INSTALL.txt file because it's just a simple copy of
the autoconf documentation and confuses users.

Change-Id: I6fd8aa13495f1238fe5c62451b95ad480b1c4bed

[ci skip]

Change-Id: I9391c09640e0b0b2b21c45a97a1fc91814d95c5d

Change-Id: Ic59d78d699af0e5f50377f83c8a7ea9a78074d81

Change-Id: I287d613fbe4180e41de67e26dfb905edeeebcf9d

in README.txt.