Merge pull request #14 from ublk-org/dev_v0.2 #107

Job	Run time
qcow2_rs windows (stable)	6m 30s
qcow2_rs ubuntu (stable)	2m 41s
build qcow2-rs on both x86_64 and i686 (stable, i686-unknown-linux-gnu)	49s
build qcow2-rs on both x86_64 and i686 (stable, x86_64-unknown-linux-gnu)	26s
build qcow2-rs on both x86_64 and i686 (nightly, i686-unknown-linux-gnu)	1m 1s
build qcow2-rs on both x86_64 and i686 (nightly, x86_64-unknown-linux-gnu)	34s
	12m 1s

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