Remove dependency on ActiveSupport

- One less dependency to manage
- Smaller deployment package for projects that depend on Consult
- Replaces String#present? by converting values to string and then checking that length is greater than 0 (nil.to_s is an empty string)
- Replaces Hash#deep_symbolize_keys! and Hash#deep_merge with their ActiveSupport implementations

lib/consult.rb

@@ -2,14 +2,14 @@
 
 require 'pathname'
 require 'yaml'
-require 'active_support/core_ext/hash'
 require 'erb'
 require 'vault'
 require 'diplomat'
 
 require 'consult/version'
 require 'consult/utilities'
 require 'consult/template'
+require_relative './support/hash_extensions'
 
 module Consult
   @config = {}
@@ -45,7 +45,7 @@ def configure_consul
       @config[:consul][:url] = ENV['CONSUL_HTTP_ADDR'] || configured_address || @config[:consul][:url]
       # If a consul token exists, treat it as special
       # See https://github.com/WeAreFarmGeek/diplomat/pull/160
-      (@config[:consul][:options] ||= {}).merge!(headers: {'X-Consul-Token' => consul_token}) if consul_token.present?
+      (@config[:consul][:options] ||= {}).merge!(headers: {'X-Consul-Token' => consul_token}) if consul_token.to_s.length > 0
 
       Diplomat.configure do |c|
         @config[:consul].each do |opt, val|

lib/support/hash_extensions.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+# ActiveSupport's corresponding methods
+#  - https://github.com/rails/rails/tree/master/activesupport/lib/active_support/core_ext/hash
+module HashExtension
+  def deep_symbolize_keys!(object = self)
+    case object
+    when Hash
+      object.keys.each do |key|
+        value = object.delete key
+        object[key.to_sym] = deep_symbolize_keys! value
+      end
+      object
+    when Array
+      object.map! { |e| deep_symbolize_keys! e }
+    else
+      object
+    end
+  end
+
+  def deep_merge(other_hash, &block)
+    merge(other_hash) do |key, this_val, other_val|
+      if this_val.is_a?(Hash) && other_val.is_a?(Hash)
+        this_val.deep_merge other_val, &block
+      elsif block_given?
+        block.call key, this_val, other_val
+      else
+        other_val
+      end
+    end
+  end
+end
+
+Hash.send(:include, HashExtension)