Silence some harmless warnings when running the tests

This happens when running the tests with Django 1.6.x on python 2.7
(Fedora 19 x86_64 in this example)
Silence "No handler found for 'cache'" style output during tests
test_functions: add tests for 10 more render functions

    - drawAsInfinite()
    - highestMax()
    - limit()
    - lineWidth()
    - removeAbovePercentile()
    - removeAboveValue()
    - removeBelowPercentile()
    - removeBelowValue()
    - secondYAxis()
    - transformNull()
functions.py: type(foo) is bar --> isinstance(foo, bar)

Also remove a few lines that are blatantly duplicated slightly above
which I'm assuming is just a copy/paste typo.
test_functions.py: more tests

    - alias()
    - aliasByNode() - needs some additional love to properly
                      verify the name when * globbing is used
                      or brackets ({}) are used in the series names.
    - aliasSub()
    - alpha()
    - color()
functions.py: Change a few map() calls to list comprehensions

list comprehensions are technically faster as they happen entirely
in C code, don't invoke a function call, and are preferred.
functions.py: add test for scale()
A few minor test updates/fixes after travis ran with python 2.6
How embarassing!
Merge branch 'master' of github.com:graphite-project/graphite-web into feature/moar-tests-and-random-cleanups
HttpRequest.raw_post_data was deprecated in Django 1.4
Merge branch 'master' of github.com:graphite-project/graphite-web into feature/moar-tests-and-random-cleanups
Remove warning silencing code

@obfuscurity's fix in #567 removes the need for this code yay!
Merge pull request #567 from obfuscurity/master

HttpRequest.raw_post_data deprecated in Django 1.4
Merge pull request #544 from SEJeff/feature/moar-tests-and-random-cleanups

Feature/moar tests and random cleanups