[#287] Add view.flot.js.

Allows flot to be used for graphs as well as
flotr2.
Based on view.graph.js in the ckan-updates branch.
[#287] Add flot view tests.

Same as view.graph.js tests (flotr2).
Merge pull request #287 from okfn/287-view-flot

[merge,view/flot][s]: Bring back graph view based on flot - thx to @johnglover.