Add an overlooked case in `google-translate-insert-nulls'.

Fixes issue #6.
Faking the "User-Agent" header is no longer necessary.

Fixes issue #5.
Don't cache the list of supported languages in a variable.

Why?  Two reasons:

(a) the computation is cheap and is hardly (if ever) noticeable;

(b) generating the list of display names of languages from the alist
    is more flexible because it allows user to customize the variable
    `google-translate-supported-languages-alist' (e.g., introduce an
    alias for a particular language, e.g. "Deutsch" for "German") and
    avoid having to update `google-translate-supported-languages'.
Bump the version number before uploading to Marmalade.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	google-translate.el
Fixed wrong reference in the doc-string.