Change: Issue Caused By Ruby Bug

Why This Change Is Necessary
========================================================================

When `require 'enumerator'` is used in code, it somehow ends up
causing `LoadError: cannot load such file -- enumerator` errors.
I believe this is caused by a [ruby issue][3] but it's since been merged
and still appears to be a problem so I'm just going to try to resolve it
myself.

What These Changes Do To Address the Issue
========================================================================

I believe this should be caused entirely by the name of the file and not
by the name of the class.  I'm going to attempt to rename the file and
see if that fixes the issue.

The `refinements.rb` file has been updated to load the proper file and
the filenames have been renamed.

Caveats
------------------------------------------------------------------------

Technically this is a backwards-incompatible change because someone
somewhere could be manually loading the refinement, but seeing as how it
is currently loaded immediately when the gem loads, I don't see that as
a common occurrence.

We are also being bad and not renaming the module to reflect the class
name, but I think it's worth it to get the fix in without a major
breaking change.

Side Effects Caused By This Change
========================================================================

Users who are manually requiring the enumerator refinement file, will
start to break.

------------------------------------------------------------------------

**Relevant URLs:**

  * [Issue Link][1]
  * [PR Link][2]
  * [Ruby Issue][3]

**Actions:**

  * Closes 175
  * Closes 176

------------------------------------------------------------------------

[1]: #175
[2]: #176
[3]: https://bugs.ruby-lang.org/issues/10902

Author: luk4s

lib/ruby-progressbar/refinements.rb

@@ -1 +1 @@
-require 'ruby-progressbar/refinements/enumerator'
+require 'ruby-progressbar/refinements/progress_enumerator'

…by-progressbar/refinements/enumerator.rb …ssbar/refinements/progress_enumerator.rblib/ruby-progressbar/refinements/enumerator.rb renamed to lib/ruby-progressbar/refinements/progress_enumerator.rb lib/ruby-progressbar/refinements/enumerator.rb renamed to lib/ruby-progressbar/refinements/progress_enumerator.rb

@@ -1,7 +1,7 @@
 if Module.private_instance_methods.include?(:using)
 
 require 'spec_helper'
-require 'ruby-progressbar/refinements/enumerator'
+require 'ruby-progressbar/refinements/progress_enumerator'
 
 class    ProgressBar
 module   Refinements