chore(readme): Fix typos in demo readme file
fix(header): Show day header on hour view and week & month headers on day view

Depending on the current view scale the day or week & month is additionally shown in the header. Otherwise it is impossible to see from day numbers only what the current month or year is.

This commit fixes a regression introduced with d83f0e3dafd92b33dff5df9915d1967cfd5b7536
fix(demo): Reload button has no functionality

Missing event handler for the reload button added. On click the sample data will be loaded again.
fix(demo): Dist files are not up to date
feat(gantt-label): Add attribute for showing or hiding column of labels

In some circumstances, for example where the screen estate is scarce, it
is useful to be able to hide the column of labels to get a better
overview. This is a missing so far.
refactor(columns): Use momentjs for column handling

This is a big refactor in column handling using momentJS features.

view-scale now supports any of momentJS unit, like year, quarter and minute.

headers-* options have been dropped, in favor of headers and headersFormats (see README).

This drops support of everything related to working hours, weekends and column-sub-scale. Those options will be replaced by #126 and #123.

Close #79
feature(calendar): Add calendar factory

This add the calendar factory, to support configuration of timeFrame, dateFrame and timeFrameMapping.

This is the primary step for "#126 Global definition of non working periods", and implements draft from gist https://gist.github.com/Toilal/5871680f0e5f2fa54412.

This also adds the first unit tests, using karma, jasmine and phantomJS, integrated in grunt default task.