Increase last.fm getting limit to 50

Closes #149.
Add basic clickstream collection

Sometimes noisy, but it works. Needs more fine-tuning.
Fix #136 (half-translucent graphs due to clicking)
Rearrange concatenation blocks in Variables tab
Add random selection from list

Closes #156.
Factor out DEFAULT_LINK_DISTANCE
Unbind hidden graphs when setting graph to display
Include hidden graphs when in isActiveGraph() check
Use setGraph() to set in newGraph() and newDiGraph()
Do not show add node/edge options if graph is hidden
Add adjacency matrix entry lookup
Numericize start and end indices for numeric for

Fixes looping forever if end is passed in as a variable.
added a 'export to python' menu item
Merge pull request #161 from Muon/master

Adjacency matrix access, basic clickstream logging and motley fixes
Explicitly check for numericity in doNumericFor

Avoids edge cases with NaN.
Add on-node-double-clicked hat block

Closes #148.
Merge pull request #162 from Muon/master

Add on node clicked, extra checks for numeric for
Convert tabs to spaces in changesToGui.js
Add manual node layout

Closes #135.
Add TMDB browser example

Closes #147.