Replacing xcodebuild with xctool on Travis CI

[chris-pilcher]

Summary of changes

• Changed tool from xcodebuild to xctool
  • The main motivation for the change was for human-friendly, ANSI-colored output. Comparison: xcodebuild output / xctool output
  • Note: I had to configure test project schemes for running so that xctool could be run
• Removed Travis CI super user requirement to speed up builds
• Added test projects that were missing from .travis.yml. The following tests were missing from .travis.yml:
  • Bounded Priority Queue
  • Counting Sort
  • Depth-First Search
  • Graph
  • Minimum Spanning Tree
  • Shortest Path
  • Topological Sort

I haven't included Treap.xcodeproj tests in the build because it is a cocoa application and causes Travis CI to terminate. This algorithm is still under construction so we can modify it before including it in our build.