upgrade luarocks

ref #822
Merge pull request #1088 from justinmk/upgradeluarocks

upgrade luarocks
test: Remove cleanup function definition from run-api-tests.exp

This function is now injected automatically when running the python-client tests
wstream: Implement wstream_set_file

It's analogous to rstream_set_file but only supports pipes(Support for regular
files may be added later). This function was added to support creating API
channels via stdout.
channel: Fix channel not being closed when the RStream reaches EOF
channel: fix channel buffer size
channel: Implement channel_from_stdio function

This function can be used to create an API channel that reads/writes from/to
stdin/stdout
api: Implement '--embedded-mode' command-line option

This option makes nvim run in "embedded mode", which creates an API channel via
stdin/stdout and disables all terminal-related code
test: Run tests in embedded mode on travis
Merge PR #1060 'Implement --embedded-mode command-line option'
clang: Null pointer passed as an argument to a 'nonnull' parameter #1090
Add 'bit' to the list of lua dependencies

- ex_cmds.lua requires the 'bit' module
Merge #1123 "Add 'bit' to the list of lua dependencies"
fileinfo: implement os_fileinfo_size

this replaces os_get_file_size and file_info.stat.st_size
fileinfo: implement os_fileinfo_hardlinks
fileinfo: implement os_fileinfo_blocksize
fileinfo: rename os_get_file_info{,_link,_fd}
fileinfo: rename os_file_info_id_equal
fileinfo: rename os_file_info_get_id
fileinfo: rename os_file_info_get_inode