Drop support for Ruby 2.3 and 2.4

With Ruby 2.3 and 2.4 being EOL, we should move our support accordingly
to keep pace with maintenance effort. This also allows simpler
interoperability with dependent gems (i.e. `nokogiri`).

Author: Tan Le

.rubocop.yml

@@ -1,5 +1,5 @@
 AllCops:
-  TargetRubyVersion: 1.9.3
+  TargetRubyVersion: 2.5.0
   # Turns off the default Rubocop rules.
   DisabledByDefault: true
   Exclude:

.travis.yml

@@ -2,8 +2,6 @@
 language: ruby
 
 rvm:
-- 2.3.0
-- 2.4.1
 - 2.5.0
 - 2.6.0
 

blob/azure-storage-blob.gemspec

@@ -38,10 +38,11 @@ Gem::Specification.new do |s|
   s.license     = "MIT"
   s.files       = `git ls-files ./lib/azure/storage/blob/`.split("\n") << "./lib/azure/storage/blob.rb"
 
-  s.required_ruby_version = ">= 2.3.0"
+  s.required_ruby_version = ">= 2.5.0"
 
   s.add_runtime_dependency("azure-storage-common",    "~> 2.0")
   s.add_runtime_dependency("nokogiri",                "~> 1", ">= 1.10.8")
+
   s.add_development_dependency("dotenv",              "~> 2.0")
   s.add_development_dependency("minitest",            "~> 5")
   s.add_development_dependency("minitest-reporters",  "~> 1")

common/azure-storage-common.gemspec

@@ -39,7 +39,7 @@ Gem::Specification.new do |s|
   s.files       = `git ls-files ./lib/azure/storage/common/`.split("\n") << "./lib/azure/storage/common.rb"
   s.files       += `git ls-files ./lib/azure/core/`.split("\n") << "./lib/azure/core.rb" << "./lib/azure/http_response_helper.rb"
 
-  s.required_ruby_version = ">= 2.3.0"
+  s.required_ruby_version = ">= 2.5.0"
 
   s.add_runtime_dependency('faraday',                 '~> 1.0')
   s.add_runtime_dependency('faraday_middleware',      "~> 1.0", ">= 1.0.0.rc1")

file/azure-storage-file.gemspec

@@ -38,7 +38,7 @@ Gem::Specification.new do |s|
   s.license     = "MIT"
   s.files       = `git ls-files ./lib/azure/storage/file`.split("\n") << "./lib/azure/storage/file.rb"
 
-  s.required_ruby_version = ">= 2.3.0"
+  s.required_ruby_version = ">= 2.5.0"
 
   s.add_runtime_dependency("azure-storage-common",    "~> 2.0")
   s.add_runtime_dependency("nokogiri",                "~> 1", ">= 1.10.8")

queue/azure-storage-queue.gemspec

@@ -38,7 +38,7 @@ Gem::Specification.new do |s|
   s.license     = "MIT"
   s.files       = `git ls-files ./lib/azure/storage/queue/`.split("\n") << "./lib/azure/storage/queue.rb"
 
-  s.required_ruby_version = ">= 2.3.0"
+  s.required_ruby_version = ">= 2.5.0"
 
   s.add_runtime_dependency("azure-storage-common",    "~> 2.0")
   s.add_runtime_dependency("nokogiri",                "~> 1", ">= 1.10.8")

table/azure-storage-table.gemspec

@@ -38,7 +38,7 @@ Gem::Specification.new do |s|
   s.license     = "MIT"
   s.files       = `git ls-files ./lib/azure/storage/table/`.split("\n") << "./lib/azure/storage/table.rb"
 
-  s.required_ruby_version = ">= 2.3.0"
+  s.required_ruby_version = ">= 2.5.0"
 
   s.add_runtime_dependency("azure-storage-common",    "~> 2.0")
   s.add_runtime_dependency("nokogiri",                "~> 1", ">= 1.10.8")