Add error-checking to bbsync.zsh; zsh snippets.

Add:
	shell_scripts/bbsync.zsh
		-Add "music_path" var to prevent hard-coded repetition of my
		music directory (which I recently renamed), should it change
		again.
		-Add a check for the existence of the music directory, to
		prevent copying if it doesn't exist.

	vim/(ultisnips/zsh.snippets, ftplugin/zsh.vim)
		-Convert zsh `iabbreviations` to snippets.
Miscellaneous mod/add to ftplugins, git, tmux.

Add:
	gitconfig, tmux.conf, vim/ftplugin/*.vim
		-Miscellaneous additions and tweaks; see the `diff`.
Add <buffer> argument to ftplugin keymaps.

Add:
	vim/ftplugin/(css, plaintex, tex).vim
		-Add `<buffer>` argument to `map` in ftplugin files, wherever it
		was missing; crucial for the times when multiple filetypes are
		loaded.
Resolve multi-filetype issue (c(pp)/html(django)).

Add:
	vimrc
		-Set multiple filetypes for `C`/`C++` and `html`/`htmldjango`
		correctly, with Vim's dotted-filetype syntax.
		-Rewrite `OpenFtpluginFile` and `OpenUltiSnipsFile` commands
		as functions that take into account dot-separated filetypes.

	vim/ftpackage/curly_bracket.vim
		-Add `<buffer>` specifiers to keymaps, as in 1d6b52f.
Add multiline visual-surround to TapSurround.

Mod:
	vim/scripts/TapSurround/autoload/TapSurround.vim
		-Modify `VisualInsertElementPair()` to support multi-line
		insertion, which it mishandled before due to an assumption of
		both visual selection start- and end- markers being on the same
		line.

Fix:
	vim/scripts/TapSurround/autoload/TapSurround.vim
		-Replace occurrence of "\w" with "\k" in
		`NormalInsertElementPair()`.
Add Synclude syntax args, completion function.

Add:
	vim/scripts/Synclude/plugin/Synclude.vim
		-Add `s:SyncludeCommandCompletion()` completion function for
		`Synclude`.
		-Redefine `SyncludeIncludeMatch()` as
		`s:SyncludeIncludeMatch()`, as global scope is unnecessary.
		-Add `syntax` command argument handling to the `Synclude`
		command, which initially only accepted `highlight` arguments.