Add option 'proc': when set to false it will not modify process.env.

[ckiickA]

Sometimes you want to only read in environment variables without modifying process.env. This is useful when reading a .env file prior to spawning a new process, for example. The 'proc' option defaults to true. If set to false, it will not modify process.env, just return the parsed object.

[coveralls]

Coverage decreased (-3.7%) to 96.296% when pulling 1ef00c8 on ckiickA:master into 825c1b2 on motdotla:master.

[maxbeatty]

the parse method is exposed to do just that

const fs = require('fs')
const dotenv = require('dotenv')
const parsedObj = dotenv.parse(fs.readFileSync('.env', { encoding: 'utf8' }))