* fix missing defaultSorted props for default sort sample
* implement customized classes for sorted header
* [test] test for sorted header classes
* implement customized style for sorted header
* [test] test for sorted header style
* update document
* add missing props check and fix typo
* seperate sorting style and header into two props
* [test] add test case if column.headerStyle and column.headerClasses were defined
* implement customized header style and classes in column level
* [test] test for customized header style and classes in column level
* [DOC] document for customized classes and styles
* sample for customized classes and styles
* typo fix for document
* tuning the wording for test and documents
* implement row seleciton style and class
* add testing for row selection style and class
* refine select row test
* add stories for row selection style and class
* add docs for row selection style and class
* patch for wrong docs
* implement cell editor style/class
* add stories for custom cell editor style and class
* patch testing for cell editor style and class
* patch docs for cell editor style and class
* implement cell editing validation
* add test cases for cell editing validation
* add story for validator for cell editor
* add docs for cell editor validation
* implement cell editor
* keyField shouldn't be editable
* add additional check to avoid some bugs
* add jsdom for enzyme mount
* add some helpers class for enzyme mounting
* add testing for cellEdit
* use npm instead
* add test for TableResolver
* table-layout: fixed; to fix the columns width when content of td changed
* add stories for cell edit
* add document for cellEdit
* implement table sort
* path for component test for table sort
* add store/base test
* add store/sort test
* add story for sort
* add column.sort and column.sortFunc
* redefine cell callback function
* it takes 4 argus `content`, `row`, `rowIndex` and `columnIndex` in
* sequence.
* [test] fix unit test for new callback
* correct the version of story for new cell callback
* [DOC] re-define structure of Contents of Table
* [DOC] update document for attrs
* re-write description for each column props
* [DOC] update document for headerCell
* re-write and add extra description for each header column props
* allow user to customize attrs for column cell
* [test] add test for customized cell attrs
* allow user to customize attrs for header column cell
* [test] add test for customized header cell attrs
* update document
* add new utils isObject and isEmptyObject
* make cell attrs lowest priority
* if style, event, classes, hidden, style was not given, display the
* HTML attributes if it's legal. However, if the attributes mentioned
* above was defined at the same time, column.attrs has lowest priority
* and it will be overwrited.
* [test] unit test for column.attrs
* [test] unit test for column.headerAttrs
* update Document
* rename story name
* fix lint error
* allow user to customize class for header cell
* add corresponding story
* allow user to customize inline-style for header cell
* add corresponding story
* [test] unit test for headerStyle
* [test] unit test for headerClasses
* update Document
