Un-deprecate use of implicit sources, by default all are used.

After much deliberation, the conclusion is that there is no good
techincal reason to enforce this, after all, and as such the decision
to deprecate it has been reverted.

CHANGELOG.md

@@ -19,9 +19,16 @@ To install or update CocoaPods see this [guide](http://docs.cocoapods.org/guides
   [Samuel Giddins](https://github.com/segiddins)
   [Molinillo#6](https://github.com/CocoaPods/Molinillo/issues/6)
 
-
 ##### Enhancements
 
+* The use of implicit sources has been un-deprecated. By default, all available
+  spec-repos will be used. There should only be a need to specify explicit
+  sources if you want to specifically _exclude_ certain spec-repos, such as the
+  `master` spec-repo, if you want to declare the order of spec look-up
+  precedence, or if you want other users of a Podfile to automatically have a
+  spec-repo cloned on `pod install`.
+  [Eloy Durán](https://github.com/alloy)
+
 * The `pod push` command has been removed as it has been deprecated in favour of
   `pod repo push` in CocoaPods 0.33.  
   [Fabio Pelosin](https://github.com/fabiopelosin)

lib/cocoapods/installer/analyzer.rb

@@ -346,8 +346,9 @@ module Pod
 
       # @!group Analysis internal products
 
-      # @return [Molinillo::DependencyGraph<Dependency>] the dependencies generated by the lockfile
-      #         that prevent the resolver to update a Pod.
+      # @return [Molinillo::DependencyGraph<Dependency>] the dependencies
+      #         generated by the lockfile that prevent the resolver to update a
+      #         Pod.
       #
       attr_reader :locked_dependencies
 
@@ -357,23 +358,17 @@ module Pod
 
       # Returns the sources used to query for specifications
       #
-      # @note Currently, this defaults to {SourcesManager.all} when no
-      #       Podfile sources are defined, but this implicit declaration of
-      #       sources is deprecated.
+      # When no explicit Podfile sources are defined, this defaults to all
+      # available sources ({SourcesManager.all}).
       #
       # @return [Array<Source>] the sources to be used in finding
-      #         specifications, as specified by the {#podfile}.
+      #         specifications, as specified by the {#podfile} or all sources.
       #
       def sources
         @sources ||= begin
           sources = podfile.sources
           if sources.empty? && !podfile.dependencies.reject(&:external_source).empty?
-            SourcesManager.all.tap do |all|
-              UI.warn all.reduce("The use of implicit sources has been " \
-                "deprecated. To continue using all of the sources currently " \
-                "on your machine, add the following to the top of your " \
-                "Podfile:\n") { |w, s| w << "\n    source '#{s.url}'" } + "\n"
-            end
+            SourcesManager.all
           else
             sources.map do |url|
               SourcesManager.find_or_create_source_with_url(url)