Added new rake tasks for running builds and tests.

- Rake build and test tasks have been added for running on the command
  line. README has been updated with the usage instructions for these
  rake tasks.

- Commands are now executed using Ruby's "system" function as opposed to
  "puts %x{}". The reasoning is that system will output both STDOUT and
  STDERR (as expected when running shell commands) whereas "puts %x{}"
  will capture STDOUT and then output to the screen upon completion of
  the command. We do not need capturing, and output is more useful as it
  lets us see what is happening as it happens.

Signed-off-by: Byron Sanchez <bfs5030@gmail.com>