Release 0.3.1

The main theme for this release is API and performance improvements.

Be aware that by way of usability improvements, a some backward compatibilities were introduced. For the details please refer to the CHANGELOG.

The highlights:

• ASN.1 types __init__(), .clone() and .subtype() signatures refactored to expect keyword arguments
• Many "getters" of ASN.1 types refactored into Python properties
• SetOf/SequenceOf ASN.1 types better mimic Python list
• The NamedValues implementation refactored to mimic Python dict
• The GeneralizedTime and UTCTime types now support to/from Python datetime object conversion
• Many minor performance improvements and bug fixes

More changes noted in the CHANGELOG.