Add installer

[matthewfeickert]

Resolves #2

[matthewfeickert]

After the make step in the install, there is a problem with the ssl module not being able to be build on LXPLUS:

Python build finished successfully!
The necessary bits to build these optional modules were not found:
_ssl                                                           
To find the necessary bits, look in setup.py in detect_modules() for the module's name.

The following modules found by detect_modules() in setup.py, have been
built by the Makefile instead, as configured by the Setup files:
_abc                  atexit                pwd                
time                                                           

Could not build the ssl module!
Python requires an OpenSSL 1.0.2 or 1.1 compatible libssl with X509_VERIFY_PARAM_set1_host().
LibreSSL 2.6.4 and earlier do not provide the necessary APIs, https://github.com/libressl-portable/portable/issues/381

EDIT: This was resolved by using a modern CentOS 7 architecture for CERN installs

[matthewfeickert]

Additionally, during make altinstall

there is a write permissions error

if test "no-framework" = "no-framework" ; then \
        /usr/bin/install -c python /usr/local/bin/python3.7m; \
    else \
        /usr/bin/install -c -s Mac/pythonw /usr/local/bin/python3.7m; \
    fi
/usr/bin/install: cannot create regular file `/usr/local/bin/python3.7m': Permission denied
make: *** [altbininstall] Error 1

this can be avoided if the --prefix option is set for ./configure.

[matthewfeickert]

c.f. @dguest's download-and-build.sh script for more on setting ssl.