bug fix & mail format check

Bugfix: 
On android 4.4, the title of idea will be refreshed by unknown reason before posting new idea.
- simple solution is to cache the content within posting new idea process

No clear information about which part is wrong when posting new idea.
- It always show uservoice connection error when user can not post new idea. Actually, this message didn`t make any sense if user forget to enter email.  So it will be more benefit for helping user check missing parts.