v0.8.0

• Encode query string params to fix invalid continuation tokens (#61)
• Reuse HTTP client (#64)
• Add a streaming Client#get_object with yields an IO (#65, #68)
• Raise proper exceptions (#66)
• Use Crystal's internal MIME registry (#67)
• Allow headers in Http#head (#69)
• Default to https (#70)
• Allow buckets to be compared by name (#72)
• Allow Bytes for upload operations (#75)