stop leaking things outside our own namespace

Also:
  - add MF.functions() to return array of functions as a string, for
    inclusion in code by MF.compile() or build() in bin/messageformat.js
  - add MF.globalName (default 'i18n') to define said global variable,
    which is also a new 3rd parameter to MessageFormat()
  - rm lib/messageformat.include.js as obsolete
  - wrap up locale loading as MF.loadLocale()
  - update examples to match changes
Merge pull request #51 from eemeli/globalize

Stop leaking things outside our own namespace