[FIX] purchase: some English errors

Courtesy of Lionel Sausin.

addons/purchase/company.py

@@ -8,8 +8,8 @@ class company(osv.osv):
     _columns = {
         'po_lead': fields.float(
             'Purchase Lead Time', required=True,
-            help="Margin of error for supplier lead times. When the system"\
-                 "generates Purchase Orders for procuring products,"\
+            help="Margin of error for supplier lead times. When the system "\
+                 "generates Purchase Orders for procuring products, "\
                  "they will be scheduled that many days earlier "\
                  "to cope with unexpected supplier delays."),
     }

addons/purchase/stock.py

@@ -174,7 +174,7 @@ class stock_picking(osv.osv):
 
     _columns = {
         'reception_to_invoice': fields.function(_get_to_invoice, type='boolean', string='Invoiceable on incoming shipment',
-               help='Does the picking contains some moves related to a purchase order invoiceable on the receipt?',
+               help='Does the picking contain some moves related to a purchase order invoiceable on the receipt?',
                store={
                    'stock.move': (_get_picking_to_recompute, ['purchase_line_id', 'picking_id'], 10),
                }),