Adding Delete() func to properties

Change-Id: Ifea9d67b6467f0373736d291a41d7d4685e697d7

properties.go

diff --git a/properties.go b/properties.go
index 6201f8b..e7cac17 100644
--- a/properties.go
+++ b/properties.go
@@ -596,6 +596,15 @@
 
 // ----------------------------------------------------------------------------
 
+// deletes the key from the map and its comments
+// abides by the rules of the builtin delete()
+func (p *Properties) Delete(key string) () {
+	delete(p.m, key)
+	delete(p.c, key)
+}
+
+// ----------------------------------------------------------------------------
+
 // check expands all values and returns an error if a circular reference or
 // a malformed expression was found.
 func (p *Properties) check() error {

properties_test.go

diff --git a/properties_test.go b/properties_test.go
index 6ae0b42..2615f32 100644
--- a/properties_test.go
+++ b/properties_test.go
@@ -797,6 +797,28 @@
 	c.Assert(func() { p.MustGetUint("max") }, PanicMatches, ".* out of range")
 }
 
+func (s *TestSuite) TestDeleteKey(c *C) {
+	input := "#comments should also be gone\nkey=to-be-deleted"
+	p, err := parse(input)
+	c.Assert(err, IsNil)
+	c.Check(len(p.m), Equals, 1)
+	c.Check(len(p.c), Equals, 1)
+	p.Delete("key")
+	c.Check(len(p.m), Equals, 0)
+	c.Check(len(p.c), Equals, 0)
+}
+
+func (s *TestSuite) TestDeleteUnknownKey(c *C) {
+	input := "#comments should also be gone\nkey=to-be-deleted"
+	p, err := parse(input)
+	c.Assert(err, IsNil)
+	c.Check(len(p.m), Equals, 1)
+	c.Check(len(p.c), Equals, 1)
+	p.Delete("wrong-key")
+	c.Check(len(p.m), Equals, 1)
+	c.Check(len(p.c), Equals, 1)
+}
+
 // ----------------------------------------------------------------------------
 
 // tests all combinations of delimiters, leading and/or trailing whitespace and newlines.