Added Installation Guide

README.md

 # tubus
-## command-line interface for video hosting services.
+### command-line interface for video hosting services.
 
 Tubus is currently a proof of concept cli interface for youtube.
 Many functions will be redone.
 
+### Installation
+```
+mkdir -p ~/go/src ~/go/pkg ~/go/bin
+GOPATH="~/go" go get gitlab.cs.fau.de/since/tubus
+```
+
+The source files will be fetched and automatically compiled.
+The resulting binary file is stored in ~/go/bin
+
+Alternatively you can clone the repository and execute 
+```
+go build
+```
+in the directory containing the source files.
+
 ### Known Bugs
 Program can crash during terminal resize if compiled with an old version of the go compiler.
+