added conditional compiling for zlib

README update

doc update

Bug fix in variable length input when write out R1 reads

by adding and modifying WriteCluster_clstronly function

minor comments

delete cd-hit-auxtools docs

since they are merged with main cd-hit docs

Update Makefile, make openmp as default

update document and README

add include<string.h> to cd-hit-auxtools/mintlib/minArray.hxx

Update the ChangeLog file.