edit readme
add Base func
edit Base.md
add clean.md
edit
~~~
add ~~~
edit
edit
 add Dir.md
add Ext.md
edit
crypto/sha256
crypto/sha512
update todo list, finish crypto/sha256 and sha512
add IsAbs.md,Join.md,Match.md,Split.md
edit match.md
edit match.md
Merge remote-tracking branch 'upstream/master'
Merge pull request #84 from zhanming/master

crpyto/sha256 and crypto/sha512