Merged #353 with changes

PR #353 implemented highlighting on search terms within search results.
This PR:

- Merges the above
- Makes a few modifications upon the implementation

Specifically, the new implementation no longer relies on hard-coded
escape-sequences. Instead, a new `highlight` function has been created,
which in turn attempts to defer to the `termcolors` library to colorize
the necessary text.

cheat/sheets.py

@@ -2,6 +2,7 @@ import os
 
 from cheat import cheatsheets
 from cheat.utils import die
+from cheat.utils import highlight
 
 def default_path():
     """ Returns the default cheatsheet path """
@@ -84,7 +85,12 @@ def search(term):
     for cheatsheet in sorted(get().items()):
         match = ''
         for line in open(cheatsheet[1]):
-            if lowered_term in line.lower():
+            if term in line:
+
+                # highlight the search term if CHEATCOLORS equals true
+                if 'CHEATCOLORS' in os.environ:
+                    line = highlight(term, line);
+
                 match += '  ' + line
 
         if match != '':

cheat/utils.py

@@ -1,8 +1,24 @@
 from __future__ import print_function
 import os
-import sys
 import subprocess
+import sys
 
+def highlight(needle, haystack):
+    """ Highlights a search term matched in a line """
+
+    # only colorize if so configured
+    if not 'CHEATCOLORS' in os.environ or os.environ.get('CHEATCOLORS') != 'true':
+        return sheet_content
+
+    try:
+        from termcolor import colored
+
+    # if pygments can't load, just return the uncolorized text
+    except ImportError:
+        return haystack
+
+    # colorize the search term, and replace it within the surrounding line
+    return haystack.replace(needle, colored(needle, 'blue'));
 
 def colorize(sheet_content):
     """ Colorizes cheatsheet content if so configured """