Merge pull request #11 from rzach/master

Changes to allow open-logic to compile out of box
fix links to GitHub in open-logic-debug
palceholder text for completeness theorem intro
add TOC to o-l-compelte and o-l-debug
Edits for Syntax & Semantics: Syntax
Edits for Syntax and Semantics: Structures for FOL

Nicoles edits + an example of a structure
More edits
added definition of modal depth
document open-logic-config.sty
Merge branch 'master' of https://github.com/OpenLogicProject/OpenLogic
change {wordy} to {explain}
add a history env for historical notes
add \args command to o-l-formulas.sty to remopve commas from list of arguments
document \arg command
document use of \args in definition of \Atom
split fol/syn/syntax.tex into smaller sections
Minor exposition and some notational fixes.
More edits

Some small stuff I need Nicole to check in here
Induction notes

Taken from Audrey's set; formatting probably needs some work to be
standardized (e.g. cases for inductive proofs)
def of substitution instance

added def of substitution instance from Aldo's notes