Swipe keyword documentation should be updated

[rz-robsn]

Since appium 1.5, the end_x and end_y parameters of the Swipe keyword on iOS refer to coordinates relative to the start_x and start_y parameters. Before 1.5, the end_ parameters used to refer to the relative to the top left corner of the screen.

The end_x and end_y parameters should be renamed to offset_x and offset_y and the keyword documentation should be updated accordingly.

See here for the counterpart of this issue on the appium python-client repo.

[serhatbolsu]

You are correct @rz-robsn this has changed with 1.5.x . We also had problem figuring this out.
Please send a pull request if you have time: also make sure to mention an example with numeric entry, such as : ${350} since robotframework default is always string

[serhatbolsu]

Fixed with #125