add missing _.intersection tests
optimized-intersection
remove unneeded other variable
remove _.index in favor of _.contains in _.intersection
use String instead of function(o){ return '' + o; }; thanks @megawac

https://github.com/jashkenas/underscore/commit/a315e9f4473005a8310540b16d565519a9556106#commitcomment-5590098
use each (rather than _.each) internally
remove aliases for _.each and _.some
remove braces
one-liner variable declarations
test node 0.10.x version on travis and update phantomjs version.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>
reference "filter" rather than its alias, "select"
clarify isEmpty in docs
use for loop in _.each even if Array.prototype.forEach is available

Currently, the behaviour of _.each depends on the availability of
Array.prototype.forEach, which can cause code to behave differently
in different environments.
remove references to native array methods
No need to escape tabs.

Literal tab characters are perfectly legal in a string literal.
A little cleanup.

Shorten long lines, extract a function, and add comments.
Conform with project style.
remove seen variable
Edit for style.
fixes #1548: _.initial broken for n > array.length