[WIP] 0.7.0: opcode trace instrumentation & plugin app architecture

[cgewecke]

#346 Swaps event-based instrumentation (with testrpc-sc) for variable-based instrumentation processed by an ethereumjs-vm opcode step listener.

The changes here are less extensive than they might seem at first glance. All the core instrumentation logic has been retained and should be +/- recognizable.

Summary

• modify injector to use variable definitions and assignment statements we can read with an opcode tracer.
• add DataCollector class which listens to the VM for data-hash-detected-on-stack 'events'
• rename instrumentSolidity --> Instrumenter & make JS class / top level controller
• rename instrumenter --> Registrar (e.g registers injection details) & make JS class.
• remove pure/view preprocessing
• mark instrumentation hits in memory / transform to coverage object from memory
• refactor test suite for this design

TO DO

• Truffle plugin
• Truffle plugin test fixtures
• Buidler plugin
• Buidler plugin test fixtures
• Address gas distortion
• Re-design & re-enable E2E tests
• New documentation (including 0.6.0 --> 0.7.0 upgrade guide)

[cgewecke]

Closing in favor of #372 (rebasing disaster)