initial formatter
give a way for reader and writer plugins
add download status
add download status
format func written
formatter in shape
tested custom handling function
test cases for formatter
improve test coverage of formatters
100% coverage
100% test coverage
tutorial for formatters
tutorial for sheet formatter
clean up file
updated readme for random access
update description of pyexcel
Merge branch 'formatter'
Merge branch 'master' into meta_coding