Fix Bazel build and update instructions.

Fix Bazel build and update instructions.

Add cmake build option.

It depends on having libev, http_parser, abseil, and openssl
all installed on the system. However for systems like
Homebrew that have all those things, it makes building
a lot simpler.

Add a --version argument.

Use new ev_io_modify method from libev.

Replace std::regex use.

A regex that worked in some places was failing on Centos.
Turns out that regex was overkill in that place.

Current stable release.