install.sh overwrites existing config, thus clobbering any user-defined options

[jkurthoconnor]

Termite draws both its user-defined aesthetics (e.g. color schemes) and its user-defined functionality from the same config file. As written, the install script running with its default option (install locally only) will simply replace an existing configuration. That would be fine if the user's existing local configuration only handled the color scheme, but that may not be an assumption worth making. (But the color scheme itself is very nice :smile: )