Fixes #28 : Support of literal strings

lexer.go

diff --git a/lexer.go b/lexer.go
index 7835116..cc4dc08 100644
--- a/lexer.go
+++ b/lexer.go
@@ -169,6 +169,8 @@
 			return l.lexComment
 		case '"':
 			return l.lexString
+		case '\'':
+			return l.lexLiteralString
 		case ',':
 			return l.lexComma
 		case '\n':
@@ -279,6 +281,29 @@
 	return l.lexRvalue
 }
 
+func (l *tomlLexer) lexLiteralString() tomlLexStateFn {
+	l.pos++
+	l.ignore()
+	growingString := ""
+
+	for {
+		if l.peek() == '\'' {
+			l.emitWithValue(tokenString, growingString)
+			l.pos++
+			l.ignore()
+			return l.lexRvalue
+		}
+
+		growingString += string(l.peek())
+
+		if l.next() == eof {
+			break
+		}
+	}
+
+	return l.errorf("unclosed string")
+}
+
 func (l *tomlLexer) lexString() tomlLexStateFn {
 	l.pos++
 	l.ignore()

lexer_test.go

diff --git a/lexer_test.go b/lexer_test.go
index cc8fb47..2555a35 100644
--- a/lexer_test.go
+++ b/lexer_test.go
@@ -460,6 +460,33 @@
 	})
 }
 
+func TestLiteralString(t *testing.T) {
+	testFlow(t, `foo = 'C:\Users\nodejs\templates'`, []token{
+		token{Position{1, 1}, tokenKey, "foo"},
+		token{Position{1, 5}, tokenEqual, "="},
+		token{Position{1, 8}, tokenString, `C:\Users\nodejs\templates`},
+		token{Position{1, 34}, tokenEOF, ""},
+	})
+	testFlow(t, `foo = '\\ServerX\admin$\system32\'`, []token{
+		token{Position{1, 1}, tokenKey, "foo"},
+		token{Position{1, 5}, tokenEqual, "="},
+		token{Position{1, 8}, tokenString, `\\ServerX\admin$\system32\`},
+		token{Position{1, 35}, tokenEOF, ""},
+	})
+	testFlow(t, `foo = 'Tom "Dubs" Preston-Werner'`, []token{
+		token{Position{1, 1}, tokenKey, "foo"},
+		token{Position{1, 5}, tokenEqual, "="},
+		token{Position{1, 8}, tokenString, `Tom "Dubs" Preston-Werner`},
+		token{Position{1, 34}, tokenEOF, ""},
+	})
+	testFlow(t, `foo = '<\i\c*\s*>'`, []token{
+		token{Position{1, 1}, tokenKey, "foo"},
+		token{Position{1, 5}, tokenEqual, "="},
+		token{Position{1, 8}, tokenString, `<\i\c*\s*>`},
+		token{Position{1, 19}, tokenEOF, ""},
+	})
+}
+
 func TestUnicodeString(t *testing.T) {
 	testFlow(t, `foo = "hello ♥ world"`, []token{
 		token{Position{1, 1}, tokenKey, "foo"},