Update LICENSE.txt for nginxparser attribution

LICENSE.txt

@@ -1,4 +1,14 @@
+Let's Encrypt Preview:
+Copyright (c) Internet Security Research Group
+Licensed Apache Version 2.0
 
+Incorporating code from nginxparser
+Copyright (c) 2014 Fatih Erikli
+Licensed MIT
+
+
+Text of Apache License
+======================
                                  Apache License
                            Version 2.0, January 2004
                         http://www.apache.org/licenses/
@@ -173,3 +183,23 @@
       defend, and hold each Contributor harmless for any liability
       incurred by, or claims asserted against, such Contributor by reason
       of your accepting any such warranty or additional liability.
+
+
+Text of MIT License
+===================
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.