rsgeo v0.1.7

• explode_lines() will expand an rs_LINESTRING or rs_MULTILINESTRING into their component segments
• Adds line_segmentize_haversine() to segment LineStrings in geographic space.
• Adds geom_line() to construct a straight line geometry between two point vectors.
• Adds coord_first(), coord_last(), coord_n(), and n_coords() functions for working with coordinates of geometries.
• Adds densify_euclidean() and densify_haversine() to densify planar and geographic linear geometries respectively.
• Bug fix: line_segmentize() would not always return n elements (h/t @Robinlovelace)
• geom_linestring(), geom_polygon() and geom_multipoint() constructors ignored order. This was due to the internal use of a HashMap. These have been swapped to a BTreeMap which preserves order. Additional tests have been added to compare tosfs constructors as validation.