Make bracket expansion smarter not at eol

E.g. "something {{ more" will become:

something {
    more
}
Don't try to use par tool if it's not installed
Forbid clang_complete auto-completion
Add <leader>oT mappings

Opens alternative file in a tab *before* the current one.
Use "//" for C++ commenting
Better terminal detection on *nix

Prefer st if available, also don't hardcode terminal emulator name.