Added original license file and updated Readme.

Signed-off-by: Michele Cattafesta <michele.cattafesta@mesta-automation.com>

License.txt

@@ -0,0 +1,8 @@
+The MIT License (MIT)
+Copyright (c) 2009 Jürgen Schildmann
+
+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.

README.md

@@ -53,5 +53,5 @@ using (var plc = new PLC(CPU_Type.S7300, deviceIpAddress, rackNumber, slotNumber
 ## Running the tests
 
 Unit tests use Snap7 server, so port 102 must be not in use.
-If you have Siemens Step7 installer, the service s7oiehsx64 has to be stopped (this is done automatically inside the constructor of the unit tests).
-You have to restart it manually if you need it.
+If you have Siemens Step7 installed, the service s7oiehsx64 is stopped when running unit tests.
+You have to restart the service manually if you need it.