Fix "file clash" bug

[nodo]

Summary

In some cases creating a file would raise an exception, due to clashes with existing file. E.g. creating a file where a directory with the same name is present.

How to reproduce the bug

$ mkdir err
$ touch er/hello
$ irb
>> require 'thor'; class A < Thor; include Thor::Actions; end; a = A.new; a.create_file('./err/hello/boom')
      create  err/hello/boom
Errno::EEXIST: File exists @ dir_s_mkdir - /Users/anodari/other_projects/thor/err/hello
from /Users/anodari/.rbenv/versions/2.4.0/lib/ruby/2.4.0/fileutils.rb:228:in `mkdir'

What happen using the bug fix

>> require './lib/thor'; class A < Thor; include Thor::Actions; end; a = A.new; a.create_file('./err/hello/boom')
  file_clash  err/hello/boom

I would be more than happy to discuss further this issue. Feel free to comment about the naming and the approach.

[nodo]

Regarding the travis checks:

• The failure for ruby 2.3.3 seems to be a known issue of rainbow gem: Gem::Ext::BuildError "can't modify frozen String" under Ruby v2.3.3 and bundler v1.14.2 ku1ik/rainbow#49

WDYT?

[rafaelfranca]

Why this was changed?

[nodo]

If say_status is before yield, in case of a conflict we have a misleading message. For instance:

create  doc/config/config.rb
file_clash  doc/config/config.rb

[rafaelfranca]

It is better to rescue the specific exception here and avoid the unless instead of the parent class.

[nodo]

Thanks for your review @rafaelfranca, sorry for the delay. I will address your comments in the next days.

[nodo]

@rafaelfranca Thanks again for your review. I have addressed you comments and rebase my branch.