Update to Truffle3, refactor CLI, add CLI unit tests, fix misc bugs

[cgewecke]

PR resolves a number of issues raised in Solcover since February 2017:

• truffle-compile hits node's memory limit (1.7MB) for very large projects.  #59 - inline assembly parsing (fixed by adding relevant AST types to the list in parse.js)
• Invalid input source specified #60 - instrumentation breaks function call chaining (see issue)
• README updates: remove require info, add memory info #61 - crashes on empty contract bodies (see issue)
• Fix istanbul exiting error introduced in #47 #51 - solc 0.4.8 - integrates adriamb's fix for the inheritance problem. You identified a caveat there. It also had a very small issue with LibraryStatements that's fixed and otherwise seems to work perfectly.
• Add gasEstimation example. Pin dev Truffle to 3.2.5 for now. #53 - solidity tests - this branch can be installed in the Truffle Metacoin project, run without configuration, have all of truffle's test pass and generate the reports without errors. Metacoin has solidity tests so maybe they won't require any special handling? Not sure.

PR makes structural changes to runCoveredTests.js (renamed exec.js for brevity).

• Target project (contracts, migrations, tests) - gets copied into a folder, instrumented and the tests run there.
• Patching is replaced with forks of testrpc, ethereumjs-vm, and provider-engine. This is done to make npm install --save-dev solcover possible. There are no guarantees that the target doesn't already include these dependencies and forking them seems to be the simplest way of scoping the assets correctly and making sure Solcover's modifications don't affect the other packages. Have added you with full admin privileges to a github org created to house them. You could fork them to Colony too though. The ethereumjs-vm there contains the patch you wrote and testrpc has been altered to have a higher default transaction gas because it looked like some transactions were running out of gas.
• Istanbul is loaded using require - again this lets npm figure out where it is / resolves problems raised if it's already one of the target's dependencies.
• Adds support for --network coverage (see README.md)
• Adds support for a small set of options loaded from a .solcover.js config file - basically testrpc options and an arbitrary test command (see README.md)
• Adds unit tests / unit test fixtures for exec.js.

PR edits README with new instructions and adds links to some example repos/reports (haven't asked any of those people for permission to be exemplified - probably bad because their tests have coverage gaps, they might be saddened by this discovery, etc.)

One test file with an intentional syntax error isn't passing the Lint CI. I've added that to an eslintignore file to no avail. Additionally, two of the tests in the cli suite are explicitly disabled in the CI context because they launch their own testrpc instances and max out CI's container memory limit. They run locally though.