Update release notes

Bump version to 2.4.0

Fixes #16

Update documentation

Fix icon disappearing on error

Merge pull request #8 from nearengine/2.2-dev

Version 2.2 Release

2.1.4 removes MtGox

Fixes issue with currency symbol

2.1.2 fixes commas and switches to MtGox HTTPS API

2.1.1 adds live prices to menu