show user defined variables to the list of completions

minor code cleanup + added profiling code

do the parsing in a web worker

added some tests that verify that values produced by customCompleter.getUserVariables(session, pos)

reusing structuredjs' copy of esprima
worker now returns list of user variables instead of the whole AST
remove console messages

build files for changes in this branch

in the process of rebasing so that this can be merged into master
modified ScratchpadAutosuggest.init to take an "options" param that should contain externalsDir and workersDir
moved the tests out of tests/output/hotnumber into tests/autosuggest

separate commit for changes to built files

changed work message type from "ast" to "userVars", updated gulpfile.js so that autosuggest tests would be run automatically, fixed paths in autosuggest/index.html