Refactor 'install_remote()'

[dy-kim]

Changes

• Making install_remote() smaller to improve readability
  • Modularize the codes of checking conditions to skip installation as a function check_if_skip_install_remote
• Remove duplicated codes in install()
  • Previously, the lines 33 ~ 39 of install-remote.R and the lines 96 ~ 102 of install.R were duplicated.
  • This update will replace those duplication as a skip_since_log_exists()
• Fix Bug in install() - Wrong argument passing in pkgbuild::rcmd_build_tools() usage #1491

[hadley]

Thanks - this should go to remotes too please.