init: enable ERE on sed with '-E' argument rather '-r'

When enabling Extended Regular Expression (ERE) on sed command, use the
'-E' argument (rather '-r') for compatibility with OS X's and BSDs' sed.

'sed -E' is used in bash and zsh completion scripts. ERE are required to
interpret alternation character '|'.

Fixes #178

init/bash_completion.in

@@ -21,7 +21,7 @@ _module_savelist() {
 }
 
 _module_not_yet_loaded() {
-    _module_avail | sort | sed -r "\%^(${LOADEDMODULES//:/|})$%d"
+    _module_avail | sort | sed -E "\%^(${LOADEDMODULES//:/|})$%d"
 }
 
 _module_long_arg_list() {

init/zsh-functions/_module

@@ -25,7 +25,7 @@ _module_savelist() {
 }
 
 _module_not_yet_loaded() {
-   _module_avail | sort | sed -r "\%^(${LOADEDMODULES//:/|})$%d"
+   _module_avail | sort | sed -E "\%^(${LOADEDMODULES//:/|})$%d"
 }