Make gettext a prerequisite rather than polluting the make file with apt commands that require sudo

.travis.yml

@@ -10,7 +10,9 @@ addons:
         -sqlite3
 
 before_install:
-    - sudo make install
+    - sudo apt-get update
+    - sudo apt-get install gettext
+    - make install
     - make migrate
     - cd InvenTree && python3 manage.py createsuperuser --username InvenTreeAdmin --email admin@inventree.com --noinput && cd ..
 

Makefile

@@ -25,7 +25,6 @@ static:
 # Install all required packages
 install:
 	pip3 install -U -r requirements.txt
-	apt-get install gettext
 	cd InvenTree && python3 setup.py
 
 # Create a superuser account

docs/start.rst

@@ -17,8 +17,9 @@ Requirements
 To install InvenTree you will need the following system components installed:
 
 * python3
-* python3-pip
+* python3-pip (pip3)
 * make
+* gettext
 
 Installation
 ------------