Set Git Gutter colours to look nicer

Git Gutter was appearing in a grey colour that make it difficult to see
the signs, updated the colours to make it easier to read.

Change-Id: I6cbee84db75fb584a5fe0cd73d6cd21d580477b9
BUG-ID:  N/A
Reverted vim theme to elflord

On setting up airline better and tried it out with elflord, decided that
it actually looked quite good and make things easier to see than the
softer colours used by the solarized theme.

Change-Id: Ifee5147cbf0e5e4b9e16b87bd26d9e43b9fc3447
BUG-ID:  N/A