update overview page
fix issue coins
Issue #79: Fix new color issuance

Changed get_previous_blockhash to get_previous_blockinfo
Added sanity check for height so we don't get in an infinite loop
Fixed a couple of dumb errors I made in colordef.py
Merge pull request #80 from jimmysong/79

Issue #79: Fix new color issuance
Merge branch 'qt' of https://github.com/fanatid/ngcccbase
gui: scan at start. fixed address retrieval
fix minor bug in output:  sometimes there is nothing to spend