Support one column in a hacky way.
Added support for single column layout with configurable vertical item spacing. Multi column layout can leave vertical item spacing property unset, and the vertical item spacing will be calculated as it was before. Single column can leave it unset, but then the spacing between items vertically will be zero.
Merge pull request #32 from kylerobson/master

Support single column and customizable vertical item spacing
Update README
Update README
Re-organize project files
added multiple sections support
Merge remote-tracking branch 'Przytua/master' into develop
Support multiple sections with header and/or footer
Update README
Update README
Add more comments into header file
Update README
Merge branch 'develop'
Update podspec
Merge branch 'feature/update_podspec' into develop
Merge branch 'develop'
Oops, I forgot to initialize sectionItemAttributes
Merge branch 'hotfix/fix_array_init'
Merge branch 'hotfix/fix_array_init' into develop