Refactor accessors so that all magic occurs in the project call. Close #699.

Accessors now have a pointer to their Plot, which allows them to dynamically
grab the right metadata.
Attach the class "baseline" to gridlines that are at x=0 or y=0, so
they can have additional styles.
Close #712
[minor] Rename ".gridlines .baseline" to ".gridlines .zeroline" as it is
more clear where it is applied and disambiguates from AreaPlot/BarPlot baseline
[minor] Adjust JSDoc formatting + variable naming per @bmalehorn's suggestions
Merge branch 'master' into accessor-refactor

Conflicts:
	plottable.d.ts
	plottable.js
	src/core/dataSource.ts
	src/utils/utils.ts
Remove warning on undefined/null data.

It incorrectly issues warnings when the plot is first loaded, due to
the default accessors returning undefinded.
Release version 0.23.1
[fix] Size legend elements correctly so they don't exceed bbox. Close #408
Release version 0.23.2
Update built files
Merge pull request #738 from palantir/baseline-gridlines

Attach the class "baseline" to gridlines that are at x=0 or y=0, so
Merge branch 'master' into accessor-refactor

Conflicts:
	plottable.js
	src/core/dataSource.ts
Merge pull request #726 from palantir/accessor-refactor

Refactor accessors so that all magic occurs in the project call. Close #...
Update README.md
Merge pull request #750 from rayshan/patch-1

Update README.md w/ quick start info
Make grunt-contrib-connect server accessible from other computers.

From their github repo:

"Setting [hostname] to '*' will make the server accessible from anywhere."
Update bower.json so as to serve our minified source too
Fix IE test failures caused by Time Axis tests choking.

Time Axis tried to set text-anchor to "left", which isn't a valid
value.
using grunt-ts@1.11.6 to use the latest version of typescript
removed extra line added by accident