Made check for customcode option more robust

Prevents PHP notice when key is not set in array.
i18n updates

* Updated gawp.pot file
* Added de_DE, el_GR, es_ES, fi, fr_FR, hu_HU & nl_NL
changed tex domain to 'google-analytics-for-wordpress' - SEE: http://ottopress.com/2013/language-packs-101-prepwork/
Merge pull request #17 from Rarst/customcode-check

Made check for customcode option more robust
Merge pull request #21 from cfoellmann/fix/i18n

text domain should be equal to the wp.org slug
Merge PR #15
Added props
Version increment to 4.3.4
Update banners in admin.
Update to version 4.3.5