Update pcl.rb

Edited to update to vtk5 and pcl-1.7.1.  This is a HEAD-only fix at the moment, the stable version fails for some reason.

I've included optional arguments for unit tests/examples and a check for sphinx-build.

Also pcl apps are now prefixed 'pcl_foo', so updated the test.

Checked on 10.8.4.
Removed newline and trailing whitespace.
Added bjensen's HEAD check for Mavericks, removed HEAD revision and updated homepage.
Merge pull request #7 from jveitchmichaelis/patch-1

Update pcl.rb