simple hack to get elastic to work with binned groups

i don't claim this is correct or general, just want to keep the conversation
moving

Conflicts:
	dc.min.js
in flattenStacks, use a set to test belonging of ordinal Xs

the previous solution in PR #251 was still using relational
operators to test whether points' x coordinates were in the domain

this is not correct for ordinal coordinates, which don't have to be
ordered by the key (the domain specifies the order, not the
relational operators)
a test for ordinal x elastic y
fix bar gap error caused by fp.precision off-by-one bug

when the domain is very close to a multiple of the precision
(which happens frequently with binning), floating point error
can cause fp.precision to deliver an x unit count that's one too high

this causes ugly big gaps between bars.
Merge pull request #298 from gordonwoodhull/ordinal-x-elastic-y-2

in flattenStacks, use a set to test belonging of ordinal Xs
Merge remote-tracking branch 'origin/pr/299'
use dc.utils.isNegligible in dc.units.fp
update d3
build docs from source
Fix #270
Merge pull request #301 from NickQiZhu/build-docs

Build docs from source
fix sourcemap - use for min only
remove vestigial getDataWithinXDomain
add .defined and .colorAccessor to line chart
run grunt default only once for web task
clean up some coloring issues and add a colorDomain function
more example
some initial work to add missing docs
start to redo tutorial as docco
add number display to api TOC
add tests for number display. Closes #291