Add alternative alias/plugin/completion configuring method.

Through configuring file .bash_profile, we can easily rebuild
our bash_it environment. Add following variable in .bash_profile:
aliases="general.aliases git.aliases"
completion="defaults.completion git.completion"
plugins="base.plugin dirs.plugin hg.plugin".

Then I can put my .bash_profile in scm repos.

bash_it.sh

@@ -44,6 +44,11 @@ do
   _load_bash_it_files $file_type
 done
 
+# Load configured aliases, completion, plugins
+load_bash_it_files "aliases" "${aliases}"
+load_bash_it_files "completion" "${completion}"
+load_bash_it_files "plugins" "${plugins}"
+
 # Load any custom aliases that the user has added
 if [ -e "${BASH_IT}/aliases/custom.aliases.bash" ]
 then

lib/helpers.bash

@@ -14,6 +14,23 @@ function _load_bash_it_files() {
   done
 }
 
+# Helper function loading various enable-able files
+function load_bash_it_files() {
+  subdirectory="$1"
+  enable_files="$2"
+  if [ ! -d "${BASH_IT}/${subdirectory}/available" ]
+  then
+    return
+  fi
+  for enable_file in ${enable_files}
+  do
+    config_file="${BASH_IT}/${subdirectory}/available/${enable_file}.bash"
+    if [ -e "${config_file}" ]; then
+      source $config_file
+    fi
+  done
+}
+
 # Function for reloading aliases
 function reload_aliases() {
   _load_bash_it_files "aliases"