Environment class does not support weather files with negative longitudes about rocketpy

[giovaniceotto]

Simple fix applied in the last commit.

The solution was to verify if a file used the range from -180 to 180 by detecting negative values in its longitude list. If so, an appropriate conversion is made to the input longitude to fall into this range (if bigger than 180). If not, the previous method is used, which was made for files ranging from 0 to 360.