Rancat

* Implements `Rancat().load_default()` which will use lorem ipsum as default text.
* Urls can now be passed to `.load`. E.g. `Rancat().load('https://myurl.com')`

* Added better user documentation
* Allows custom phrase structure via `RanCat().load_structure(*args)` where args are either filepaths (str) or iterables of strings (tuples, lists)
* `rancat.conversions` provides a number of functions that can be passed to `RanCat.set_conversion`
* Fixed issue where `RanCat().hard_reset()` did not return the RanCat object. This is fixed and can hence be used in chained commands.

* Allows use of own conversion function via `RanCat().set_convert_func(FUNC)`
* Allows use as an iterator `for x in <rancat instance>: ...`
* Allows uniqueness to be guarenteed through `RanCat(unique=True)` or `RanCat().set_unique(True)`, defaults to False
* Allows chaining of some commands, `RanCat().set_unique(True).set_convert_func(FUNC).load(...).load(...)`
* Files are now semi-lazily evaluated, iterative read size can be set via `RanCat(read_size=num_lines)` or `RanCat().set_read_size(num_lines)`
* Allows the use of the same datafile multiple times
* Supports `RanCat().soft_reset()` which will reset the combinations being produced but not the files being used.
* Supports `RanCat().hard_reset()` which performs a soft reset as well as resetting all files being used.