make `generate_protoc_files` work with Windows and Linux
Merge pull request #225 from BergWerkGIS/master

make prebuild step `generate_protoc_files` platform independent
upgrade to node-pre-gyp 0.5.0
touchup readme
build against mapnik master (3.x)
build against both gcc and clang
travis cleanup
fix travis syntax
add source build to readme - closes #226
bump package.json to v1.4.1-alpha
working on Windows build script.
windows build script: added 'npm install -g node-gyp'
account for mapnik 2.2.0 and 2.3.0 SDK.
first working version.
add code comment about visibility after https://github.com/joyent/node/commit/bd8a5755dceda415eee147bc06574f5a30abb0d0#commitcomment-5686345
changed encoding of mapnik_settings.js to UTF8.
path to protoc.exe missing in PATH.
typo when adding BASE_DIR to PATH.
testing S3
using node-pre-gyp for S3