Add LINQ-like macros and functions and some chaining examples.
Readme tweak.
Fix a bug in `@transform` when it's called as a macro.
Support Associative types with `@transform`.
Readme updates.
First (broken) attempt at changing linq names and trying a different `@select`.
Updated function and macro names; added `@withfirst` and an alternate
definition of `@where` based on that.
Change idx to ix.
Update the readme, and add speedtests.
Merge pull request #3 from JuliaStats/linq

LINQ-like additions