Add basic gruvbox light theme using 256 colors

Add basic gitignore file
Add opening config files in correct vim file-types
Exclude vim file artifacts
Fix dark theme against changes in tmux v2.9
Fix typos
Improve plugin installer
Update README
Update changes to gruvbox dark theme
Update config and remove deprecated/outdated configuration
Update tmux-gruvbox-dark.conf

gruvbox-tpm.tmux

@@ -1,4 +1,25 @@
 #!/usr/bin/env bash
 
 CURRENT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-tmux source-file "$CURRENT_DIR/tmux-gruvbox-dark.conf"
+THEME_OPTION="@tmux-gruvbox"
+DEFAULT_THEME="dark"
+
+get_theme() {
+	local option="$1"
+	local default_value="$2"
+	local option_value
+  option_value=$(tmux show-option -gqv "$option")
+	if [ -z "$option_value" ]; then
+		print "$default_value"
+	else
+		print "$option_value"
+	fi
+}
+
+main() {
+	local theme
+  theme=$(get_theme "$THEME_OPTION" "$DEFAULT_THEME")
+	tmux source-file "$CURRENT_DIR/tmux-gruvbox-${theme}.conf"
+}
+
+main