Switch from solparse to solidity-parser

[cgewecke]

It looks like solparse is getting integrated into solidity-parser (see here) and other parser fixes are being channelled there as well. For example this change to allow expressions as modifier arguments is needed to be able to run against functions like this in zeppelin-solidity where sha3 is invoked within a modifier call.

This PR:

• replaces solparse with solidity-parser in package.json (fetching from the github master)
• requires and runs solidity-parser in instrumentSolidity.js.
• checks for and ignores contract-level variable declarations. Solidity-parser differs from solparse in that it groups these together in a sub-array like a block statement. Solcover currently expects the contract body to be all objects and throws an error when it hits the array. I don't think this change alters current behavior - e.g. top level var declarations aren't being instrumented.