Feature/fix deprecations

[hez]

Fixes a bunch of deprecation warnings with newer Elixir. Tested with OTP 22 and Elixir 1.10.2.

The largest of the changes is moving from Dict.merge/2 to Map.merge/2. I believe this should work, the same tests are failing in this branch as master.

Copy of the deprecations fixed:

warning: parentheses are required when piping into a function call. For example:

    foo 1 |> bar 2 |> baz 3

is ambiguous and should be written as

    foo(1) |> bar(2) |> baz(3)

Ambiguous pipe found at:
  lib/ex_minimatch/compiler.ex:163

warning: module attribute @re_specials was set but never used
  lib/ex_minimatch/matcher.ex:10

warning: module attribute @two_star_no_dot was set but never used
  lib/ex_minimatch/matcher.ex:9

warning: module attribute @two_star_dot was set but never used
  lib/ex_minimatch/matcher.ex:8

warning: module attribute @star was set but never used
  lib/ex_minimatch/matcher.ex:7

warning: module attribute @qmark was set but never used
  lib/ex_minimatch/matcher.ex:5

warning: module attribute @two_star_no_dot was set but never used
  lib/ex_minimatch/compiler.ex:10

warning: module attribute @two_star_dot was set but never used
  lib/ex_minimatch/compiler.ex:9

warning: Dict.merge/2 is deprecated. Use the Map module for working with maps or the Keyword module for working with keyword lists
  lib/ex_minimatch.ex:134: ExMinimatch.compile/2

warning: Dict.merge/2 is deprecated. Use the Map module for working with maps or the Keyword module for working with keyword lists
  lib/ex_minimatch/matcher.ex:ExMinimatch.Matcher.match_regex_parts/1

warning: Dict.merge/2 is deprecated. Use the Map module for working with maps or the Keyword module for working with keyword lists
Found at 7 locations:
  lib/ex_minimatch/compiler.ex:ExMinimatch.Compiler.clear_state_char/1
  lib/ex_minimatch/compiler.ex:ExMinimatch.Compiler.handle_dot_start/1
  lib/ex_minimatch/compiler.ex:ExMinimatch.Compiler.handle_open_class/1
  lib/ex_minimatch/compiler.ex:ExMinimatch.Compiler.handle_trailing_things/1
  lib/ex_minimatch/compiler.ex:ExMinimatch.Compiler.handle_weird_end/1
  lib/ex_minimatch/compiler.ex:ExMinimatch.Compiler.move_to_next/1
  lib/ex_minimatch/compiler.ex:ExMinimatch.Compiler.parse/1