Fix build and test process

[conradwt]

This PR fixes the build and test process for macOS.

Enhancements

• Fix: macOS install command doesn't have a -t option

• added make rule to install dependent shards

OS Tested

macOS 10.14 Status

• installed successfully

• tests ran successfully

Ubuntu 18.04 Status

• installed successfully

• tests ran successfully

[ysbaddaden]

Thanks, but the only change I will merge is the install -t removal.

1. Please don't bump VERSION (mark the changelog as UNRELEASED);
2. The bin/shards target shouln't be changed to shards otherwise it will always rebuild;
3. Shards mustn't be installed on the system before running tests. Only integration tests need it and searched it the local bin folder.

[ysbaddaden]

I misread. Running bin/shards install manully once ain't much of an hassle to be capable to run tests, but it's a pain when developing to have it run each time, because it will try to update the remote git repository on each test run.

[conradwt]

@ysbaddaden Should I mark the CHANGELOG as follows:

## v0.8.2 (UNRELEASED)

or

## v0.8.2 [UNRELEASED]

[conradwt]

@ysbaddaden I'm in the process of building a Portfile for shards. Now, Travis CI is failing because
minitest isn't installed. Also, MacPorts will break as well because make test will be ran as part of the port build process. For now, I'll update the Travis CI to run tests as follows:

make install_shards test

This will give developers like yourself good testing experience when using make test and this will make Travis CI happy. I guess a longer term solution would be to use the default testing framework for Crystal. The Crystal Book mentions spec module.

[conradwt]

@ysbaddaden Please let me know if there's anything else I need to do with this PR because I need to get this one published to complete work on the Amber MacPorts Portfile.

[ysbaddaden]

Merged as 1d249fb.