Style stuff
Add .gitignore
PEP8 (sorry, it hurts working on non-PEP8-compliant code)
Rewrite insert nums logic completely

Now uses str.format() for formatting and allows specification of a format
string in the prompt. Furthermore, the step is now specified by ":" and may be
omitted.
Only supports numerics as of now, but can do prefixed hexadecimal 8-digit
output using "1~#010x", for example. Yeah, really powerful.

Also includes a basic syntax definition for the format syntax which I used as
base for the regular expression. Most parts are copied from the Pythons syntax
definition in order to be compatible with it.
Add alpha support for new format syntax

Also introduce a new "w" (wrap) settings which will result in the patterns
being wrapped if they exceed the start value's length.
And improve parsing of the repository.
Convert start value to float by default if step is a float
Update Readme
Allow negative values for start and step
Add option to fill the regions in reversed order
Update format_syntax for the latest changes
Make the sign optional in exponentfloat
Regression fix for the "reverse" addition

Introduced by a99f132f686c19499e06217d8ad3d9bfec9c6560.

`self.view.sel()` in fact returns an interator (or, "RegionSet"s behave like
iterators) which would adapt to changes from `view.replace()`. However, if we
construct the region list before making the changes this will be skipped.