ci: Switch to codecov.io for coverage data

Continue uploading to coveralls, for now, so we can compare the
services.

.codecov.yml

@@ -0,0 +1,23 @@
+codecov:
+  notify:
+    require_ci_to_pass: yes
+
+coverage:
+  precision: 2
+  round: down
+  range: "70...100"
+
+  status:
+    project: yes
+    patch: yes
+    changes: no
+
+parsers:
+  gcov:
+    branch_detection:
+      conditional: yes
+      loop: yes
+      method: no
+      macro: no
+
+comment: off

README.md

@@ -8,7 +8,7 @@
 
 [![Travis Build Status](https://travis-ci.org/neovim/neovim.svg?branch=master)](https://travis-ci.org/neovim/neovim)
 [![AppVeyor Build status](https://ci.appveyor.com/api/projects/status/urdqjrik5u521fac/branch/master?svg=true)](https://ci.appveyor.com/project/neovim/neovim/branch/master)
-[![Coverage Status](https://img.shields.io/coveralls/neovim/neovim.svg)](https://coveralls.io/r/neovim/neovim)
+[![codecov](https://img.shields.io/codecov/c/github/neovim/neovim.svg)](https://codecov.io/gh/neovim/neovim)
 [![Coverity Scan Build](https://scan.coverity.com/projects/2227/badge.svg)](https://scan.coverity.com/projects/2227)
 [![Clang Scan Build](https://neovim.io/doc/reports/clang/badge.svg)](https://neovim.io/doc/reports/clang)
 [![PVS-studio Check](https://neovim.io/doc/reports/pvs/badge.svg)](https://neovim.io/doc/reports/pvs)

ci/after_success.sh

@@ -5,4 +5,5 @@ set -o pipefail
 
 if [[ -n "${GCOV}" ]]; then
   coveralls --gcov "$(which "${GCOV}")" --encoding iso-8859-1 || echo 'coveralls upload failed.'
+  bash <(curl -s https://codecov.io/bash) || echo 'codecov upload failed.'
 fi