[Specification] Allow the name_and_version_from_string regex to match spaces
[SpecificationSpec] Add specs covering spaces in subspecs and special characters
[Changelog] Add entry for fixing the reading of subspecs with spaces from Lockfiles.
Merge pull request #179 from CocoaPods/regex-spaces

[Specification] Allow the name_and_version_from_string regex to match spaces
Update podfile syntax reference on branches and tags

Adding information from the [_using_ guide](https://github.com/CocoaPods/guides.cocoapods.org/blob/master/source/using/the-podfile.html.md) which tells how to use a specific branch or tag

As a side note, generating the same documentation from two files (the comments here and the Markdown in the guides repo) that aren't kept in sync seems like it could be made better. Confusing to have conflicting (or at least non-matching) doc pages, the way that [the syntax page](http://guides.cocoapods.org/syntax/podfile.html#pod) and [the using page](http://guides.cocoapods.org/using/the-podfile.html) are now.
[Set] Sources are used in the order in which they are provided
[Style] Fixes two RuboCop offenses
[Specification::Source::Aggregate] Updates spec for https://github.com/CocoaPods/Core/pull/181
[Set] Fix for relying on hash key order as the order of sources
[Source::Aggregate] Fix for relying on hash key order for the sources provided to Sets
Merge pull request #180 from mrh-is/patch-1

[Documentation] Update podfile syntax reference on branches and tags
[Style] Processed feedback from @segiddins on https://github.com/CocoaPods/Core/pull/181
[Source] Remove the notion of a `DataProvider` and move logic into `Source`
[Source] Remove default repo path value in initializer
[Source] Optimize #search to avoid iterating through all available sets
Merge pull request #184 from CocoaPods/remove-data-provider

[Source] Remove the notion of a `DataProvider` and move logic into `Source`
Merge pull request #181 from Thomvis/issue/CocoaPods/2556

[Set] Sources are used in the order in which they are provided
[CHANGELOG] List enhancement as an enhancement
Ensure that we raise when attempting to stub an undefined method
[Source] Fix issue with spec repo without git remote

https://github.com/CocoaPods/CocoaPods/issues/2590