Drop support for Py2.5

[dbrgn]

After the discussion in #159 where we decided to deprecate 2.5, in #203 @davidhalter mentioned that 2.5 is not supported anymore with the new tokenizer.

Dropping 2.5 support would be fine with me. In that case I'd go through the codebase to find things that we can change (e.g. removing simplejson) and adjust tests / docs.

@tkf @davidhalter ack?

[davidhalter]

yes. please do that.

[tkf]

Glad that we are finally dropping 2.5

[davidhalter]

:)

[dbrgn]

"13 changed files with 23 additions and 128 deletions" - oh yeah!