Update ch1.md

Converted the Abstract Syntax Tree definition to use HTML tags instead of Markdown, looks like github's markdown have the same issue than Stack Overflow's http://meta.stackexchange.com/questions/51404/markdown-handles-inline-bold-text-within-a-word-incorrectly
types+grammar: clarifying note on parseFloat in ch4
core: adding cover art to main README
types+grammar: added lots of discussion to 'implicit coercion' of ch4
types+grammar: lots more in ch4 about implicit coercion, incl 'logical or' and 'logical and' operators, null/undefined, etc
types+grammar: ch4, adding spec quote about logical-or and logical-and operators behavior
types+grammar: clarifying 'ToPrimitive' abstract operation across ch4
types+grammar: few tweaks/clarifications in ch3
types+grammar: little bit of text in ch4 implicit coercion sections
types+grammar: more for ch4, on true vs. false with == loose equality
types+grammar: more on true/false == stuff in ch4
Merge pull request #175 from rlbisbe/master

Changed Markdown for HTML to get AST definition properly rendered
types+grammar: tweaks to wording in ch4
types+grammar: ch4, more structure/content
types+grammar: ch4 tweaks
types+grammar: ch4, clarifying ==, ===, and their negations
types+grammar: ch4 correcting misstatements about == on two objects
types+grammar: ch4, adding discussion of objects-to-not-objects, and covering 'abstract relational' algorithm
types+grammar: ch4, more on unary operator coercion with - and +
types+grammar: ch4 more on < operator weirdness