fix bug when parsing spreadsheets with text box
Address issue 32.
Implement the fix for a file with no sharedStrings.xml as proposed by
HeinOldewage.
Resolve conflicts
Merge branch 'llehouerou-absolutepath-workbookrel'
Merge branch 'master' of https://github.com/shawnps/xlsx into shawnps-master
Handle case where there are rows with no cells.
Merge branch 'shawnps-master'
add travis.yml
Merge pull request #42 from shawnps/add-travis-yml

add travis.yml