Feat: Add option for custom regexp

[hacke2]

1. 'Object.assign' replace 'JSON.parse(JSON.tringify(opts))'
2. support custom rImages regexp

Resolve zckrs/gulp-css-base64#28

[hacke2]

@zckrs

[zckrs]

https://travis-ci.org/zckrs/gulp-css-base64/jobs/122771422#L504

[hacke2]

I can't find the .eslintrc in gulp-css-base64

[zckrs]

eslintrc is deprecated

see https://github.com/zckrs/gulp-css-base64/blob/master/package.json#L49

[coveralls]

Coverage remained the same at 99.13% when pulling 3117bef695c78092fb98c6d9bd3622800734b93e on hacke2:master into b63225ede3ed711e579fb0b7ca09ff16ddae6221 on zckrs:master.

[hacke2]

I forget has Node version less than 4...My company used 4 or 5....

[zckrs]

Yeah :S sorry. Actually this plugin work well with 0.12 and 0.10.

[zckrs]

You should remove Object.assign :S

[hacke2]

Why do you think should not modify original options object?

[zckrs]

IMO if you want pass regex in json option you should use new RegExp constructor and toString

[hacke2]

User must use string replace regex in option?

[coveralls]

Coverage increased (+0.007%) to 99.138% when pulling fb0d3e0cee92d158b2076eac96b7d3fab739e0ce on hacke2:master into b63225ede3ed711e579fb0b7ca09ff16ddae6221 on zckrs:master.

[coveralls]

Coverage increased (+0.007%) to 99.138% when pulling d77188eeb6aeb2aeda33fee086638241fb8ff189 on hacke2:master into b63225ede3ed711e579fb0b7ca09ff16ddae6221 on zckrs:master.

[coveralls]

Coverage remained the same at 99.13% when pulling 46c1c6a1f9e5ccb05fc323676c8693b3b0d0a6f9 on hacke2:master into b63225ede3ed711e579fb0b7ca09ff16ddae6221 on zckrs:master.

[coveralls]

Coverage remained the same at 99.13% when pulling c8259f1ddc6bf3327c87931a5e52a038f2abbf02 on hacke2:master into b63225ede3ed711e579fb0b7ca09ff16ddae6221 on zckrs:master.