Silence warnings being emitted when running tests

[Alhadis]

I saw these warnings as I was running tests for #4133:

lib/linguist/heuristics.rb:414: warning: character class has duplicated range: /[A-Z\.][\w\d\.]*:{/
lib/linguist/language.rb:504: warning: assigned but unused variable - filenames

They're trivial but still unrelated to what #4133 is doing, so I siphoned these changes off to a separate PR. :-) Explanation of changes:

warning: character class has duplicated range: /[A-Z\.][\w\d\.]*:{/

That's happening because \w already covers the character ranges that \d does. Using them together in a bracketed character class is therefore redundant.

I also removed the backslash from the dots too, because hold no special meaning when used within a character class. It wouldn't make sense for it to match any single character in a defined subset of specific characters you're trying to match. =)

warning: assigned but unused variable - filenames

Admittedly, I don't even know what this line is doing:

filenames = Samples.cache['filenames']

But I didn't wanna remove it in case it was there to deliberately invoke a side-effect by accessing Samples.cache['filenames']. But I wanted it to shut up so I found a way to make it "used" by sprucing up a conditional assignment:

-    if interpreters == nil	+    interpreters = {} if interpreters.nil?
-      interpreters = {}	+    filenames    = {} if filenames.nil?
-    end
+    interpreters = {} if interpreters.nil?
+    filenames    = {} if filenames.nil?

Which inevitably lead to me polishing whitespace elsewhere in the file, as you'll see by the diffs. 😁 I'd apologise for being a neat-freak, but you guys know I'm not actually sorry. ❤️

[pchaigno]

This is safe to remove. I forgot to do it in 0bf4b8a.

[Alhadis]

Perfect! Works for me. 😀 Consider it gone, and my drastic spike of Ruby fluency to be concerning

(for me)

[Alhadis]

And don't worry, I did double-check the ||= operator to guarantee it did what I thought it does. 😉

There's no good reason I should be this good at Ruby, I'm always bitching about why its ecosystem are the antichrist 😢

[lildude]

And if by magic, all the Linguist-related warnings are gone. LGTM. 🙇

[Alhadis]

Now we just need to get Charlock Holmes to STFU about that encoding variable not being initialised. 😂👌