Storage C++ Client Library (Lite) v0.3.0

Changes in v0.3:

• Parallel blob uploading & downloading
• Proxy support
• Configurable retry policy
• Default retry count is changed from 25 to 3
• Sample for blob_client
• Type of size parameter in upload/download APIs is changed from size_t to uint64_t
• Fix authentication issues when running against Azurite and IoT devices
• Bug fix: error information isn't populated if libcurl fails
• Bug fix: downloading empty blob fails
• Bug fix: duplicate HTTP headers in retry requests