Define vim mappings for creating/moving past {}s.

Ctrl-k : insert 'k'urly brackets. A ';' is added after the '}' if a struct/class/enum/union is being defined.
jj : continue insertion after current block.

Stopped using Snipmate. I had experimented with Ultisnips ('https://github.com/SirVer/ultisnips.git'), then decided my new mappings for creating/moving past blocks enclosed in {}s meant I could do without snippets.