Fix readme markdown

README.md

 Casaubon is a static site generator written in Rust. I had very specific goals in mind when writing Casaubon and it is not meant to be all things for all people. Casaubon does what it is intended to do and no more.
 
 Goals
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 - Convention over configuration
 - Learn Rust
 - Fast compile times
 
 Non-goals
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 - Extensibility
 - Flexibility