feat(limitTo): limitTo filter accepts strings

[jtymes]

This allows strings to be filtered by limitTo, using the same methods

Closes #653

[IgorMinar]

LGTM otherwise. can you please fix the issues and push update to this branch?

[jtymes]

@IgorMinar Should be good now.

[pkozlowski-opensource]

@jtymes Just pushed it to a test branch and getting tests failures on IE8:

IE 8.0 (Windows) Filter: limitTo should return the last X items when X is negative FAILED
    Expected 'tuvwxyz' to equal 'xyz'.
    Expected 'tuvwxyz' to equal 'xyz'

I guess that the reason is this one: http://stackoverflow.com/a/6918982/1418796
Could you try to change it to make IE8 happy and re-submit? Thnx!

[jtymes]

@pkozlowski-opensource Darn you windows people ;) I'll fix it up!

[pkozlowski-opensource]

Landed as 9e96d98. Thank you!