Release 1.1.0

• Improvements to thread safety of LinkInfo and its ancestors.
• Eliminate queueing and retry of /v1/url requests. A long link will now be
  generated immediately on any request failure.

This required some changes to the public interface of BaseEvent. The return
types of getCustomData() and name() have changed to avoid returning
pointers or references to unsynchronized objects from synchronized getters.

BranchIO::JSONObject getCustomData() const;
std::string name() const;

In addition, the destructor of LinkInfo will now block while any background
request is in progress. Once createUrl() is called, the LinkInfo object
is guaranteed to outlive the thread that executes the request. To force
immediate termination of the background thread, use LinkInfo::cancel().

Also note that each LinkInfo instance can currently only be used once to
generate a URL. For now, create a new LinkInfo instance for each URL
request. This will be improved in a future release. Each LinkInfo
instance is reusable.