check_compatibility! breaks if @executables contains Pathname objects

[djungowski]

This is what we encountered:

Poltergeist uses cliver since 1.4.0. We set
poltergeist_options[:phantomjs] =
With a pathname object, leading to a lot of errors:

 NoMethodError: undefined method `[]' for #<Pathname:0x007ff093b69028>
 occurred at /Users/djungowski/.rvm/gems/ruby-2.0.0-p247/gems/cliver-0.3.2/lib/cliver/dependency.rb:71:in `block in check_compatibility!'

This is because the check_compatibility! method expects a string. It would be good if the method either supports the Pathname object (which would be useful) or uses a .to_s

[yaauie]

The YARDDOC explicitly says that executables should be [String,Array<String>], so with the current version you have to comply. I would welcome a pull-request that relaxes that to [String,Pathname,Array<String,Pathname> so long as it doesn't explicitly require 'pathname'. I would rather not support [#to_s,Array<#to_s>] since just about everything has #to_s.

[djungowski]

Since the method uses paths it would be nice if it could support the Pathname object in the long run. Would at least make sense if you ask me ;-)

[yaauie]

It would be nice, but would be a breaking change since we currently support 1.8.7 & it doesn't have Pathname.