add support for computing and verifying file checksums (supported: adler32, crc32, md5, sha1)
add 'checksums' easyconfig parameter
log MD5 checksum for source and patch files, verify checksum for source and patch files if it's provided
add unit tests for checksum functionality
fix remarks
add support for using 'size' as checksum, add support for specifying multiple checksums per file
make sure OAuth token can be supplied for tests that talk to GitHub, to avoid strict API rate limits
Merge pull request #774 from boegel/checksums

add support for computing and verifying source/patch file checksums