Update install.rst
Update install.rst

This is a small change, only relevant when you already have pip installed on the system (e.g /usr/bin/pip) and this is incompatible with python 2.7 (like having an old version of pip for python 2.6)
If the ~/.local/bin path is appended in $PATH rather than prepended, the pip file from the system will be used instead and some errors due to version conflicts can appear in that case.
matz-e/lobster,matz-e/lobster,matz-e/lobster