Assert _each loops over all elements
make _.each return obj, small optimizations
add _.till / _.untill
fix isArrayLike
use nativeIsArray, natives are garanteed to exist in this version of underscore
optimize isType methods
native functions are garanteed to exist in this version, so take advantage, use hasOwnProperty instead of _.has
optimize _.map and use local 'map' function internally
optimize _.bind and natively use fn.bind
use nativeKeys
remove a TODO comment
created optimized _.findKey
Notes for possible other implimentation of _.isNaN
optimize _.pick
add _.extendIfNull
tweak compose
optimize _.intersection and _.difference
tweak _.shuffle
use till internally to optimize _.contains and _.every
use findKey in _.some