Doc: Document how to use the yamllint Python module

docs/development.rst

@@ -1,5 +1,11 @@
 Development
 ===========
 
+yamllint provides both a script and a Python module. The latter can be used to
+write your own linting tools:
+
+.. autoclass:: yamllint.errors.LintProblem
+   :members:
+
 .. automodule:: yamllint
    :members:

yamllint/errors.py

@@ -16,10 +16,15 @@
 
 
 class LintProblem(object):
+    """Represents a linting problem found by yamllint."""
     def __init__(self, line, column, desc='<no description>', rule=None):
+        #: Line on which the problem was found (starting at 1)
         self.line = line
+        #: Column on which the problem was found (starting at 1)
         self.column = column
+        #: Human-readable description of the problem
         self.desc = desc
+        #: Identifier of the rule that detected the problem
         self.rule = rule
         self.level = None