Added contributors to README
Fixed Oleg Geiers Twitter name
Updated Package name in README
access to Default Hotkey
Added InsertNums to tools menu
Added @anthillape to contributors list
Code cleanup (and adjust name)
Add expression evaluation capability

Syntax is "<start>[:<step>][~<format>][::<expr>][!]"
(e.g. `0~#010x::1<<i`).
Update README with the new expression feature
Make the <start> part optional (for numeric mode)
Remove TODOs since I actually implemented them
Fix alpha mode that broke with the expr addition
Rearrange some utility functions (to the top)
Bug fixes

- Actually allow an empty format string (since we made all the effort
  for <start> to be optional)
- Do not override `0` with `1` for <start>
Add preview for the input panel

Automatically updates and cleans up undo stack (works on cancel too).

Also fixes a regression with alpha mode.