luajr 0.1.8

• The Lua "io" library is now capable of getting input from the R console
  (e.g. with io.read()) -- previously, trying this would cause R to hang
  (at least from RStudio).

• The Lua os.exit() function now ends Lua execution without crashing RStudio.

• lua_shell() now stores commands in the R console history.

• The luajr build process now skips making libluajit.so and the luajit
  executable, as these are not needed for luajr.

• Corrected an oversight in the documentation for lua_shell(); this fixes
  issue #3. Thanks to
  @SugarRayLua for bringing my attention to this!

• Addressed some further issues turned up by CRAN checks.