Add wrappers for strip commands so that files are copied to the
local drive before stripped.

Stripping files on a local folder instead of a Virtualbox shared folder
is needed to work around this bug: https://www.virtualbox.org/ticket/8463
Use absolute path to strip_wrapper because bootstrap.sh is started with
pwd /home/vagrant while vagrant up.
Merge pull request #4 from larskanis/use-wrappers-for-strip

Add wrappers for strip commands so that files are copied to the local drive before stripped.
Strip debug symbols from sample gem

This relates to tjschuck/rake-compiler-dev-box#4, as strip seems
to have issues working with VirtualBox shared folder mechanism.

Testing this first will help us implement the wrappers descrived
in the above ticket.
Whitespace :scissors:
Use all available CPU cores for compiling
Use a extraced directory of tar instead of the downloaded file to trigger
setup of mingw-w64 compilers.

This should decrease issues with broken downloads.
Also install Ruby 2.1.0
Install rake-compiler on all installed Rubies
Adjust Ruby for cross-ruby 1.8.7
Bump Ruby 1.9.3 and 2.0.0 to latest patchlevel

- 1.9.3-p484
- 2.0.0-p353
cross-compile Ruby 2.1.0 too

Do not cross-compile extensions for 2.1 (yet)
Avoid running compilation every time

Place a checkpoint file and verify it before attempting to install
gems or cross-compile Rubies.
RVM already install bundler for us
Use RubyGems spec loading mechanism
Drop x86-mswin32-60 support

The above platform was only necessary during the transition time of
One-Click Ruby Installer (OCI) to RubyInstaller back when 1.8.6
was released.

That was 7 years ago and had to die at some point, why not now?