Add a few __delitem__ implementations

Lib/fontTools/ttLib/tables/C_O_L_R_.py

@@ -138,6 +138,9 @@ class table_C_O_L_R_(DefaultTable.DefaultTable):
 		elif glyphSelector in self.ColorLayers:
 			del self.ColorLayers[glyphSelector]
 
+	def __delitem__(self, glyphSelector):
+		del self.ColorLayers[glyphSelector]
+
 class LayerRecord(object):
 
 	def __init__(self, name = None, colorID = None):

Lib/fontTools/ttLib/tables/V_O_R_G_.py

@@ -115,6 +115,9 @@ class table_V_O_R_G_(DefaultTable.DefaultTable):
 		elif glyphSelector in self.VOriginRecords:
 			del self.VOriginRecords[glyphSelector]
 
+	def __delitem__(self, glyphSelector):
+		del self.VOriginRecords[glyphSelector]
+
 class VOriginRecord(object):
 
 	def __init__(self, name = None, vOrigin = None):

Lib/fontTools/ttLib/tables/_g_l_y_f.py

@@ -991,6 +991,8 @@ class GlyphCoordinates(object):
 	def __setitem__(self, k, v):
 		if isinstance(k, slice):
 			indices = range(*k.indices(len(self)))
+			# XXX This only works if len(v) == len(indices)
+			# TODO Implement __delitem__
 			for j,i in enumerate(indices):
 				self[i] = v[j]
 			return

Lib/fontTools/ttLib/tables/_h_m_t_x.py

@@ -91,6 +91,9 @@ class table__h_m_t_x(DefaultTable.DefaultTable):
 			self.metrics[attrs["name"]] = [safeEval(attrs[self.advanceName]), 
 					safeEval(attrs[self.sideBearingName])]
 
+	def __delitem__(self, glyphName):
+		del self.metrics[glyphName]
+	
 	def __getitem__(self, glyphName):
 		return self.metrics[glyphName]