Add ability to compile only some files in an upload

[egelmex]

During an upload I would like the option to only some of the uploaded files.

[kmpm]

Can you think of a way of how those parameters should look on the command line. It's doable but I can't imagine a way that would not mess things up.

[egelmex]

Good point, I will have a think about it.

[benrussell]

./nodemcu-uploader.py upload init.lua:init.lc

[benrussell]

or, new tool: ./nodemcu-compiler.py init.lua:init.lc

This would be my preference.

[kmpm]

Ok. I will not make a new tool. Detecting if a file called init.lua should be saved as init.lc could be done. If you come with a pull request I will use it but since I am somewhat short on time I will not do it now.