Use text instead of string as sqlite type

Ref: crystal-lang/crystal-db#71

README.md

@@ -20,7 +20,7 @@ dependencies:
 require "sqlite3"
 
 DB.open "sqlite3://./data.db" do |db|
-  db.exec "create table contacts (name string, age integer)"
+  db.exec "create table contacts (name text, age integer)"
   db.exec "insert into contacts values (?, ?)", "John Doe", 30
 
   args = [] of DB::Any

samples/memory.cr

@@ -2,7 +2,7 @@ require "db"
 require "../src/sqlite3"
 
 DB.open "sqlite3://%3Amemory%3A" do |db|
-  db.exec "create table contacts (name string, age integer)"
+  db.exec "create table contacts (name text, age integer)"
   db.exec "insert into contacts values (?, ?)", "John Doe", 30
 
   args = [] of DB::Any

spec/connection_spec.cr

@@ -14,7 +14,7 @@ describe Connection do
   it "opens a database and then backs it up to another db" do
     with_db do |db|
       with_db("./test2.db") do |backup_db|
-        db.exec "create table person (name string, age integer)"
+        db.exec "create table person (name text, age integer)"
         db.exec "insert into person values (\"foo\", 10)"
 
         dump db, backup_db
@@ -32,7 +32,7 @@ describe Connection do
   it "opens a database, inserts records, dumps to an in-memory db, insers some more, then dumps to the source" do
     with_db do |db|
       with_mem_db do |in_memory_db|
-        db.exec "create table person (name string, age integer)"
+        db.exec "create table person (name text, age integer)"
         db.exec "insert into person values (\"foo\", 10)"
         dump db, in_memory_db
 
@@ -48,7 +48,7 @@ describe Connection do
   it "opens a database, inserts records (>1024K), and dumps to an in-memory db" do
     with_db do |db|
       with_mem_db do |in_memory_db|
-        db.exec "create table person (name string, age integer)"
+        db.exec "create table person (name text, age integer)"
         db.transaction do |tx|
           100_000.times { tx.connection.exec "insert into person values (\"foo\", 10)" }
         end
@@ -62,7 +62,7 @@ describe Connection do
     with_cnn do |cnn|
       cnn.should be_a(SQLite3::Connection)
 
-      cnn.exec "create table person (name string, age integer)"
+      cnn.exec "create table person (name text, age integer)"
       cnn.exec "insert into person values (\"foo\", 10)"
 
       cnn.scalar("select count(*) from person").should eq(1)

spec/db_spec.cr

@@ -80,7 +80,7 @@ DB::DriverSpecs(DB::Any).run do
   end
 
   it "gets last insert row id", prepared: :both do |db|
-    db.exec "create table person (name string, age integer)"
+    db.exec "create table person (name text, age integer)"
     db.exec %(insert into person values ("foo", 10))
     res = db.exec %(insert into person values ("foo", 10))
     res.last_insert_id.should eq(2)