Please Consider Update README

[wxk6b1203]

Test platform: win10 x64

Reproduce: use sample code from readme

import asn1

encoder = asn1.Encoder()
encoder.start()
encoder.write('1.2.3', asn1.ObjectIdentifier)
encoded_bytes = encoder.output()

As is runed from the latest branch master, ObjectIdentifier does not inside asn1, instead, in asn1.Numbers
Change

encoder.write('1.2.3', asn1.ObjectIdentifier)

to

encoder.write('1.2.3', asn1.Numbers.ObjectIdentifier)

That works.

[andrivet]

Fixed, thanks for reporting this mistake.