lua filename is always used in lowercase (--to=FileName.lua)

[jankatins]

If I use '--to' with a lua file, the lua filename must be lowercase otherwise it fails because it searches for the lowercase filename:

λ pandoc --print-default-data-file sample.lua > /tmp/sample_LUA.lua     
λ echo '# Title' | pandoc --from 'markdown' --to /tmp/sample_LUA.lua
pandoc: /tmp/sample_lua.lua: openFile: does not exist (No such file or directory)
λ mv /tmp/sample_LUA.lua /tmp/sample_lua.lua 
λ echo '# Title' | pandoc --from 'markdown' --to /tmp/sample_lua.lua
<h1 id="title">Title</h1>

Original issue: JessicaTegner/pypandoc#156

[jankatins]

Could be c8f97d3

I ran the test with:

λ pandoc --version                                                
pandoc 2.1.3
Compiled with pandoc-types 1.17.4.2, texmath 0.10.1.1, skylighting 0.7.0.2
[...]

[link2xt]

@jankatins I almost fixed it. The problem is not with this commit, though it adds a TODO ("-- note: use non-lowercased version writerName") that was never resolved.