Started implementing IAM role credential source
Implemented simple buffer datatype
Modified existing code to use new buffer functionality
Removed unneeded strings functions
Added buffer clearing functionality
More work on IAM role credential source; modified to use buffer
Merge branch 'feature/buffer'
Style tweaks: rearranged headers &c.
Migrated remaining string helper method to join buffer functionality
Moved cURL functionality into separate file
Added check for libcurl to autotools configuration