Fix typos in API documentation (#2041)

Author: yvonnefroehlich

pygmt/helpers/decorators.py

@@ -49,7 +49,7 @@
             is no fill.""",
     "I": r"""
         spacing : str
-            *xinc*\ [**+e**\|\ **n**][/\ *yinc*\ [**+e**\|\ **n**]].
+            *x_inc*\ [**+e**\|\ **n**][/\ *y_inc*\ [**+e**\|\ **n**]].
             *x_inc* [and optionally *y_inc*] is the grid spacing.
 
             - **Geographical (degrees) coordinates**: Optionally, append an

pygmt/src/coast.py

@@ -39,7 +39,7 @@
 @kwargs_to_strings(R="sequence", c="sequence_comma", p="sequence")
 def coast(self, **kwargs):
     r"""
-    Plot continents, shorelines, rivers, and borders on maps
+    Plot continents, shorelines, rivers, and borders on maps.
 
     Plots grayshaded, colored, or textured land-masses [or water-masses] on
     maps and [optionally] draws coastlines, rivers, and political

pygmt/src/contour.py

@@ -86,7 +86,7 @@ def contour(self, data=None, x=None, y=None, z=None, **kwargs):
     I : bool
         Color the triangles using CPT.
     triangular_mesh_pen : str
-        Pen to draw the underlying triangulation [Default is none].
+        Pen to draw the underlying triangulation [Default is None].
     no_clip : bool
         Do NOT clip contours or image at the boundaries [Default will clip
         to fit inside region].