Allow specifying compile_commmands.json location
Allow specifying compile_commmands.json location

This adds support for the standard libTooling option '-p', to specify
the directory containing compile_commands.json. oclint already supports
this option, but oclint-json-compilation-database doesn't.

Fixes oclint/oclint#435.
Fixes oclint/oclint-json-compilation-database#9.

oclint/oclint-json-compilation-database