feat(espower): use `escallmatch` module to describe target patterns
feat(espower): option `powerAssertVariableName` does not required any more
feat(espower): support chained callee like `browser.assert.element(selector)`
refactor(escallmatch): eliminate duplication
Merge pull request #10 from twada/escallmatch

[WIP] Use escallmatch module to describe instrumentation target patterns.