Make general-purpose-overlay the default modal
Extract findUnusedAddress function
Use hive-convert for btcToSatoshi

Also remove unnecessary big.js imports
First time sync also iterate through change addresses to find the first unused
Generate new change address on send
Make testnet work with blockr API

Also, fixes address parsing from transaction
[#76]
Modal prevents scroll
remove console log of transactions
Move gulp-sketch to dependency for heroku
Upgrade browserify and gulp-browserify to fix buffer bug
adjust easing and css for dropdowns
animate arrow on dropdowns
set sidebar elements to flexbox layout
tidy code and deps for velocity
adjust timing and css after review