Release cleancall 0.1.2

[gaborcsardi]

Prepare for release:

• devtools::check_win_devel()
• rhub::check_for_cran()
• rhub::check(platform = "solaris-x86-patched")
• rhub::check(platform = "ubuntu-rchk")
• rhub::check_with_valgrind()
• rhub::check_with_sanitizers() Included in check_for_cran().
• Polish NEWS

Perform release:

• Bump version (in DESCRIPTION and NEWS)
• Submit to CRAN
• Approve email

Wait for CRAN...

• Tag release
• Bump dev version

Template from r-lib/usethis#338