Remove the .spl file from the repository.

[brobeson]

• [x] Try to remove the file, and it' history, since it's a binary file. If not possible, just git rm the file.
• [ ] Add a method to rebuild the .spl file when Vim is started. See this SO for ideas: https://stackoverflow.com/questions/27240638/is-there-a-quick-way-to-rebuild-spell-files-from-wordlists
• [ ] Add .spl files to git ignore.