Revert partial Makefile tweaks _only_ for travis

In an effort not to repeat ourselves, let's try to limit the one-off
tasks that are solely for Travis build output formatting.

Partial revert of e71dafda2
Use xcpretty conditionally for make targetswhen installed

If xcpretty is installed, it'll received the piped output of xcodebuild for the
play, mac, ios, and test Makefile targets. When xcpretty is not installed,
we'll just fall back to the regular xcodebuild output.

This builds off of @pietbrauer's xcpretty work starting in 93743f31.
Merge pull request #19 from andrewsardone/travis-and-makefile-cleanup

Conditional xcpretty-ing in Makefile, single build targets for travis