feat: adds pgsql compatibility (#72)

database/migrations/2021_02_25_041246_create_splits_table.php

@@ -18,11 +18,9 @@ class CreateSplitsTable extends Migration
         Schema::create('splits', function (Blueprint $table) {
             $table->uuid('id')->primary();
             $table->date('date');
-            $table->string('symbol', 15);
+            $table->string('symbol', 25);
             $table->float('split_amount', 12, 4);
             $table->timestamps();
-
-            $table->foreign('symbol')->references('symbol')->on('market_data');
         });
     }