Add support for %w and %W (words) sigils with return type modifiers

[devinus]

As discussed previously in #501, %w can now return a few core data types other than just binaries (extendible to support further types in the future without breaking backwards compatibility). My enthusiasm for this jumped ten-fold now that I'm writing things that could be written like this:

fields %w(
  contact_id
  contact_guid
  brand_id
  title
  first_name
  middle_name
  last_name
  suffix
  eligibility_mask
  username
  user_password
  dob
  gender
  passport_country
  password_number
)a

[yrashk]

👍 👍 👍

[meh]

Nice stuff 👍

[alexrp]

nitpick: backticks

[devinus]

@alexrp On %w ?

[alexrp]

yep

[devinus]

@alexrp I thought so too but I was mimicking the other sigil @doc's. Lets add backticks for all of them in a separate patch.

[josevalim]

String.split was merged. Maybe we could get rid of String.split_words and just call String.split or lc(part inlist String.split(...), do: ...) depending on the modifier?

[yrashk]

@devinus bump?

[devinus]

@yrashk Yep, today.

[devinus]

@josevalim @yrashk All suggestions implemented. I like this version a lot.