First attempt at error handling using Either, I'm not satisfied with it though
Merge branch 'master' into either
More intuitive name
Preprocessor returns Seq[Result[LogicalLine]] instead of Result[Seq[LogicalLine]], so that we can emit both the preprocessor error and later errors
Newline node is obsolete
MathCompiler can report up to one error per logical line (though InlineParser won't pass them on)
Update documentation
Code generator function generates one node at a time, in preparation to convert to Result/Either
Correctly report physical line numbers in `Failure`s
Bugfix with previous commit
MathExpr nodes retain position information, at least relative to their logical line
I think I'm going to have to give up on satisfying IntelliJ
Added upper elements to int and sum.  Fixed #47
... compiles to /hdots.  Closes #33
Tests the set macro

closes #38
fixed gitignore for ignoring vim swap files
Compile the * symbol to \\times

Closes #41
Adds shortcuts for a variety of symbols

Closes #46
empty equations no longer break LaTeX

Closes #31
fixed typo