Assert: fixed exception() return with user handler [Closes #149]
CommandLine: added support for enumerated option

Option specified as '-p <a|b>' must be 'a' or 'b'.
Option specified as '-p [a|b]' must be 'a' or 'b' or without value.
Added option -o (output format), option --tap deprecated [Closes #146]

The option -o can enumerates from:
  console: the same as default, but logo is not printed
  tap: replacement for the --tap option (Test Anything Protocol)
  none: nothing is printed, only bad usage errors when occures
Merge pull request #155 from milo/pull-output-option

Option -o (output format)
Merge pull request #150 from milo/pull-fix-149

Assert: fixed exception() return
Added PhpExecutable, abstracted from ZendPhpExecutable
Rename PhpExecutable to ZendPhpExecutable
Added HhvmPhpExecutable, added detection for php/hhvm binary type
Enable HHVM runs on Travis
Merge pull request #156 from Majkl578/feature/hhvm-fixes-v2

HHVM support & compatibility v2