Add fish shell completions: options & all themes autocompletion (#49)

* Add completions/fish/base16-universal-manager.fish

Allows for autocompletion of commands and available themes

* README:Add 'Shell completions' section under 'Installation'

README.md

@@ -89,6 +89,11 @@ go build
 
 If you get errors on missing dependencies, install them as usual with `go get`.
 
+### Shell completions
+* [fish shell](https://github.com/fish-shell/fish-shell) completions: Add the [`completions/fish/base16-universal-manager.fish`](completions/fish/base16-universal-manager.fish) to `~/.config/fish/completions/`
+
+      wget https://raw.githubusercontent.com/pinpox/base16-universal-manager/master/completions/fish/base16-universal-manager.fish -O ~/.config/fish/completions/base16-universal-manager.fish
+
 ## Usage
 
 To run, just execute the application without any command line flags. It will

completions/fish/base16-universal-manager.fish

@@ -0,0 +1,17 @@
+# Fish completions for base16-universal-manager
+
+# Never complete with filenames
+complete -f -c base16-universal-manager -d "A command line tool to install base16 templates and set themes globally"
+
+# Complete available themes
+set -l themes_list (sed -n 's/^\(.*\).yaml:.*/\1/p' ~/.cache/base16-universal-manager/schemeslist.yaml)
+complete -f -c base16-universal-manager -n "__fish_seen_subcommand_from --scheme; and test (count (commandline -opc)) -eq 2" -a "$themes_list"
+
+# Description for each command
+set -l base16_universal_manager_commands (base16-universal-manager --help-long | sed -En 's/^  (--(\w-?)+).*/\1/p')
+set -l base16_universal_manager_commands_help (base16-universal-manager --help-long | sed 1,3d | sed -En 's/.{21}([A-Z].*)/\1/p')
+set -l i 1
+for command in $base16_universal_manager_commands
+    complete -f -c base16-universal-manager -n "not __fish_seen_subcommand_from $base16_universal_manager_commands" -a "$command" -d "$base16_universal_manager_commands_help[$i]"
+    set -l i (math $i + 1)
+end