updated readme
Squashed 'dependencies/lmdb/' content from commit 335f0e4

git-subtree-dir: dependencies/lmdb
git-subtree-split: 335f0e4ceeed82a1302bf16cf2c3df00f45798c4
fixed whitespace in binding.gyp
build on OS X

Requires clang for C++11 support, hence the xcode_settings.
adjusted node-lmdb.h and binding.gyp for the bundled lmdb
fixed examples