WORK plugin added

* before definition of zsh plugins set WORKPLUGIN_DIRS variable with
  list of your "work" directories relative to your $HOME, such as
  WORKPLUGIN_DIRS=('work' 'src')
* now you can use work command in your zshell, which will change CWD to
  first occurrence WORKPLUGIN_DIRS sub folders
* directories competition is supported
* also, you can define WORKPLUGIN_CALLBACK function, which will be
  called after directory change. In my case, I use it to call
  virtualenvwrapper's `workon` function

plugins/work/work.plugin.zsh

@@ -0,0 +1,27 @@
+typeset -A _WORKPLUGIN_DIRS_FULLPATH
+
+for dir in $WORKPLUGIN_DIRS; do
+    _WORKPLUGIN_DIRS_FULLPATH[$dir]="$HOME/$dir"
+done
+
+work() {
+    local dir
+    for dir in $_WORKPLUGIN_DIRS_FULLPATH; do
+        if [[ -d "$dir/$1" ]]; then
+            builtin cd "$dir/$1"
+            break
+        fi
+    done
+    if [[ $(type -w "WORKPLUGIN_CALLBACK") == "WORKPLUGIN_CALLBACK: function" ]]; then
+        WORKPLUGIN_CALLBACK "$1"
+    fi
+}
+
+_work_comp() {
+    local dir
+    for dir in $_WORKPLUGIN_DIRS_FULLPATH; do
+        compadd $(ls $dir)
+    done
+}
+
+compdef _work_comp work