Continuous integration with Appveyor

Closes #1526

appveyor-build.cmd

@@ -0,0 +1,8 @@
+@echo off
+
+cd scintilla\boostregex                                                                 || exit
+buildboost.bat C:\projects\notepad-plus-plus\boost_1_55_0                               || exit
+cd ..\win32                                                                             || exit
+nmake -f scintilla.mak                                                                  || exit
+cd ..\..\PowerEditor\visual.net                                                         || exit
+msbuild notepadPlus.vcxproj /p:configuration="Unicode Debug" /p:platform=Win32          || exit

appveyor.yml

@@ -0,0 +1,8 @@
+clone_depth: 1
+
+install:
+  - ps: Invoke-WebRequest -OutFile boost_1_55_0.7z -UserAgent Wget/1.17.1 https://sourceforge.net/projects/boost/files/boost/1.55.0/boost_1_55_0.7z
+  - 7z x boost_1_55_0.7z 2>nul >nul
+
+build_script:
+  - cmd /k "C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\bin\vcvars32.bat" < appveyor-build.cmd