Use {tic} for continous integration

.Rbuildignore

@@ -3,3 +3,4 @@
 ^\.travis\.yml$
 LICENSE\.md
 ^appveyor\.yml$
+^tic\.R$

.gitignore

@@ -4,3 +4,4 @@
 .Ruserdata
 .DS_Store
 ._*
+docs/

tic.R

@@ -0,0 +1,8 @@
+# installs dependencies, runs R CMD check, runs covr::codecov()
+do_package_checks()
+
+if (ci_on_travis() && ci_has_env("BUILD_PKGDOWN")) {
+  # creates pkgdown site and pushes to gh-pages branch
+  # only for the runner with the "BUILD_PKGDOWN" env var set
+  do_pkgdown()
+}