Fixes: clarify install instructions and reactivate external program checks

README.rst

@@ -49,11 +49,13 @@ Install
 
 Download OCRmyPDF here: https://github.com/fritz-hh/OCRmyPDF/releases
 
-To install, extract the release files and run::
+To install, download the tarball and run:
 
-    pip install .
+    pip install ocrmypdf-3.0rc2.tar.gz
 
-Run::
+You can install it within a virtual environment or system-wide.
+
+To run the program::
    
    ocrmypdf --help
 

setup.py

@@ -129,7 +129,7 @@ def check_external_program(
 command = next((arg for arg in sys.argv[1:] if not arg.startswith('-')), '')
 
 if command.startswith('install') or \
-        command in ['check', 'test', 'nosetests', 'easy_install']:
+        command in ['check', 'test', 'nosetests', 'easy_install', 'egg_info']:
     check_external_program(
         program='tesseract',
         minimum_version='3.02.02',