Fixed the check of the IO verbosity

Symfony Console 2.3+ supports setting higher verbosity levels than VERBOSE so the isVerbose implementation needs to use an inequality rather than an equality for the condition.

Note that running ``phpspec run -v`` or ``phpspec run -vv`` or ``phpspec run -vvv`` will always give you the same output (after this change), because PhpSpec does not take advantage of the extra verbosity levels to add more output.

Before this change, ``phpspec run -vv`` or ``phpspec run -vvv`` would display the non-verbose output (too much verbosity kills the verbosity)
This would make more sense to me the other way around - not sure why

'The level VERBOSE should be less than or equal to the selected level'
vs
'The selected level should be greater than or equal to VERBOSE'