Default Std

• make std default feature (#130 #131)
• macro use cleanup (#125)
• remove rustc_serialize support (#112)
• make rand a private dependency
• fix some doc rendering issues
• bump sha-1 to 0.4 (#110)
• rename use_std to std (#107)
• Add tests for compact/readable representations (#105)
• Remove use of serde_test (#104)
• Add impl fmt::{UpperHex,LowerHex} for {Uuid,Hyphenated,Simple} (#103)