Move string patching into env
Merge branch 'master' of github.com:mongodb/bson-ruby
RUBY-632 adding license/copyright source headers to all non-trival files

Per recommendations the apache 2.0 license policies, all non-trivial source files *should* contain source file headers with licensing and copyright information.
RUBY-632 adding full copy of the apache 2.0 license

Per Apache 2.0 license requirements, we *must* have a full copy of the software license in root directy of our codebase. Permissible file names for this copy of the license are LICENSE or LICENSE.txt.
RUBY-632 adding notice file for copyright info

Per the Apache 2.0 license requirements, we *must* provide a NOTICE file in the root of our codebase containing our own copyright information as well as the license and copyright information from any 3rd-party dependencies being distributed with our code.

All dependencies for this project are currently non-bundled so this requirement is satisified simply by including our own copyright information here.