fix issue of pie chart being invisible when total group value is 0
Test and linted
Added support for RequireJS AMD.
table header moved to dc.js

Still allows original example to function as-is.
Allows non-hard-coded table column headers.
Fixes bug 497.  Changed baseMixin filterHandler to correctly handle filtering dates.  We use a trick from Crossfilter 'a <= b && a >= b' instead of 'a == b' because the former coerces the values to primitives which then works for dates.
Moves references to dc.renderAll or dc.redrawAll to _chart.redrawGroup & _chart.renderGroup respectively.  More conventional with other charts and allows easier overriding.
Exposing filter functions for easier overrides
Minor fixes to removeFilter and hasFilter that are congruent with the changes in filterHandler.  filters may be dates, thus indexOf will not work.
changed data-table to support dynamically set columns for table header

Supplied 3 examples of setting the columns; the original method, which
requires the fixed html code for thead/cols; another which uses mostly
the data element names which become capitalized as col headings, and
another where most of the columns have the column label specified along
with an accessor function. There is some code to strip a
numberFormat/etc from a function converted to string, an attempt to
auto-generate a column header from a function, in data-table.js,
columnString().
fixing unintended checkins
updated stock example via grunt
attempt again, renderedstockfixture
attempt3 after installing saucelab; touched data-table.js
retry 4. connected sauce
Merge branch 'master' into fix_bug_497
Merge branch 'master' into expose_filter_functions
Merge master
Fixes row test case that was comparing key values of the SVG to the filters.  The key is numeric and not a string.
review changes

Restored index.html, no need for a change.
Added 4th example of columns.
updated restored stock example