ustc_cas v0.2.0

• follow api change of CAS

Full Changelog: v0.1.4...v0.2.0

ustc_cas v0.1.4

• fix configuration of docs.rs build

ustc_cas v0.1.3

• change bytes into optional dependency used by validate-code feature
• add blocking feature providing blocking version of get_ticket

Full Changelog: v0.1.2...v0.1.3

ustc_cas v0.1.2

• make validate code recognition a feature
• add minimal supported rust version