update flow inspector to use Epicenter's /v2/model/introspect

[mmrj]

this means:

• update flow inspector bookmarklet to determine if we're using epicenter.js < 2.0, in which case, solve flow inspector: for epicenter.js 2.0, is trying to pull the model file from the static directory #88 and flow inspector: not pulling authorization information correctly (file lookup is 401) #89 but otherwise unchanged
• update flow inspector bookmarklet to determine if we're using epicenter.js >= 2.0, in which case, use introspection instead
• declare that flow.js 0.11.0 is ONLY compatible with epicenter.js >= 2.0

note that together, these mean holding release of flow.js 0.11.0 until after v1.43 (introduction of instropection)

[narenranjit]

This is actually not relevant - the introspection API returns back all variable names in the model, which we actually already have (since it's in the UI). The context shows the equations which the introspect api won't provide. This may be useful for showing which of the variables in your UI are not present in the model, so I'll leave it open for that purpose.