[ruby/csv] Do not loop forever when skip_lines regexp matches zero length with anchors (#110)

* Do not loop forever when skip_lines regexp matches zero length with anchors

* Remove needless white spaces

* Add missing eos check in skip_needless_lines

* Simplify test

https://github.com/ruby/csv/commit/3b15d4a3e8

lib/csv/parser.rb

@@ -769,7 +769,7 @@ class CSV
     def skip_needless_lines
       return unless @skip_lines
 
-      while true
+      until @scanner.eos?
         @scanner.keep_start
         line = @scanner.scan_all(@not_line_end) || "".encode(@encoding)
         line << @row_separator if parse_row_end

test/csv/parse/test_skip_lines.rb

@@ -102,4 +102,11 @@ class TestCSVParseSkipLines < Test::Unit::TestCase
                              :skip_lines => /\A#/))
     end
   end
+
+  def test_empty_line_and_liberal_parsing
+    assert_equal([["a", "b"]],
+                 CSV.parse("a,b\n",
+                           :liberal_parsing => true,
+                           :skip_lines => /^$/))
+  end
 end