changed yticks; updated test images

See merge request flatland/flatland!7

delete temporary image files

See merge request flatland/flatland!6

Rendering test updates - more test images

See merge request flatland/flatland!5

created folder flatland/images/test

moved xticks, yticks to middle of grid squares
added more image tests

Rendering

See merge request flatland/flatland!4

Simple test for environment consistency

See merge request flatland/flatland!3

Test rail env

See merge request flatland/flatland!2