Fix `cleanfigure`'s `handle` validator

USing `ishandle` to determine whether a handle is being passed.
Before, `isnumeric` was used, this is wrong and breaks in R2014b.

The right function to use would be `ishghandle`, but since I'm unsure this works
in Octave or old MATLAB versions, `ishandle` is used.
The difference between both should only be noticable for Simulink objects,
which is outside our scope anyhow
Merge branch 'fixHG2'
nschloe -> matlab2tikz
Merge pull request #472 from nschloe/nschloe-fixes

nschloe -> matlab2tikz
remove hint about minimal Pgfplots version
fix a handful of md5sums
tests: replace error-prone tan-sin-cos function
updating md5sums
skip failing octave test
Move test suites to separate directory.

Beware, this will break test execution for most people.
Make sure to add `./test/suites` to your path to overcome this!!
Remove broken `pointReductionTest`

Eventually, we should make a similar test, but right now this
function is completely broken and small enough to discard.
Rebuilding from scratch should be the way to go.
Rename `matlab2tikz_acidtest` -> `testMatlab2tikz`

It was never a real ACID test anyhow. For compatibility, leave
`@ACID` as the default test case, though.
Document changes in test in README