Lookup and activate versions of system installed gems

If BEXT_ACTIVATE_VERSIONS is set, bundler_ext will use
linux_admin to retrieve the versions of gems installed
with rpm/dpkg (or yum/apt). bundler_ext will then attempt
to activate those specific versions before proceeding.
Merge pull request #12 from movitto/activate-system

Lookup and activate versions of system installed gems
Shorten default ENV variable names to 'BEXT'

Expanded names are still supported for
compatability reasons
Merge pull request #13 from movitto/bext-rename

Shorten ENV variable names to 'BEXT'
Bump version for release 0.3.2
Refactor bundler_ext into smaller modules
Replace linux_admin dep w/ direct call to package system

linux_admin has its own deps which may conflict with the
deps being activated by bundler ext
Add BundlerExt#system_setup analogous to Bundler#setup
Merge pull request #14 from movitto/bext_setup

bundler_ext refactoring