use double backticks more uniformly (#240)

this changes single quotes to double backticks for operators and
functions in the user guide, and in code comments.

see discussion at
#201 (reply in thread)

doc/user_guide.rst

@@ -72,8 +72,8 @@ Basic math with uncertain Variables
 =========================================
 
 Uncertainties variables created in :func:`ufloat` or :func:`ufloat_fromstr` can
-be used in basic mathematical calculations ('+', '-', '*', '/', '**') as with
-other Python numbers and variables.
+be used in basic mathematical calculations (``+``, ``-``, ``*``, ``/``, ``**``)
+as with other Python numbers and variables.
 
 >>> t = ufloat(0.2, 0.01)
 >>> double = 2.0*t
@@ -160,18 +160,18 @@ are found in the :mod:`uncertainties.umath` module:
 
 The functions in the :mod:`uncertainties.umath` module include:
 
-    'acos', 'acosh', 'asin', 'asinh', 'atan', 'atan2', 'atanh',
-    'ceil', 'copysign', 'cos', 'cosh', 'degrees', 'erf', 'erfc',
-    'exp', 'expm1', 'fabs', 'factorial', 'floor', 'fmod',
-    'frexp', 'fsum', 'gamma', 'hypot', 'isinf', 'isnan',
-    'ldexp', 'lgamma', 'log', 'log10', 'log1p', 'modf',
-    'pow', 'radians', 'sin', 'sinh', 'sqrt', 'tan', 'tanh', 'trunc'
+    ``acos``, ``acosh``, ``asin``, ``asinh``, ``atan``, ``atan2``, ``atanh``,
+    ``ceil``, ``copysign``, ``cos``, ``cosh``, ``degrees``, ``erf``, ``erfc``,
+    ``exp``, ``expm1``, ``fabs``, ``factorial``, ``floor``, ``fmod``,
+    ``frexp``, ``fsum``, ``gamma``, ``hypot``, ``isinf``, ``isnan``,
+    ``ldexp``, ``lgamma``, ``log``, ``log10``, ``log1p``, ``modf``,
+    ``pow``, ``radians``, ``sin``, ``sinh``, ``sqrt``, ``tan``, ``tanh``, ``trunc``
 
 
 Comparison operators
 ====================
 
-Comparison operators ('==', '!=', '>', '<', '>=', and '<=') for Variables with
+Comparison operators (``==``, ``!=``, ``>``, ``<``, ``>=``, and ``<=``) for Variables with
 uncertainties are somewhat complicated, and need special attention.  As we
 hinted at above, and will explore in more detail below and in the
 :ref:`Technical Guide <comparison_operators>`, this relates to the correlation

uncertainties/__init__.py

@@ -177,15 +177,15 @@
 approximated by a line around 0), which might not be precise enough
 for all applications.
 
-- Comparison operations (>, ==, etc.) on numbers with uncertainties
+- Comparison operations (``>``, ``==``, etc.) on numbers with uncertainties
 have a pragmatic semantics, in this package: numbers with
 uncertainties can be used wherever Python numbers are used, most of
 the time with a result identical to the one that would be obtained
 with their nominal value only.  However, since the objects defined in
 this module represent probability distributions and not pure numbers,
 comparison operator are interpreted in a specific way.
 
-The result of a comparison operation ("==", ">", etc.) is defined so as
+The result of a comparison operation (``==``, ``>``, etc.) is defined so as
 to be essentially consistent with the requirement that uncertainties
 be small: the value of a comparison operation is True only if the
 operation yields True for all infinitesimal variations of its random
@@ -204,7 +204,7 @@
 variables that almost never give the same value.  However, x == x
 still holds.
 
-The boolean value (bool(x), "if x...") of a number with uncertainty x
+The boolean value (bool(x), ``if x...``) of a number with uncertainty x
 is the result of x != 0.
 
 - The uncertainties package is for Python 2.3 and above.