Add support for parsing dependencies from platformio.ini

[andrew]

Docs: http://docs.platformio.org/en/latest/projectconf.html

Example:

[platformio]
env_default = nodemcuv2

; You MUST inject these options into [env:] section
; using ${common_env_data.***} (see below)
[common_env_data]
build_flags = -D VERSION=1.2.3 -D DEBUG=1
lib_deps_builtin =
    SPI
    Wire
lib_deps_external =
    ArduinoJson@~5.6,!=5.4
    https://github.com/gioblu/PJON.git#v2.0
    https://github.com/adafruit/DHT-sensor-library/archive/master.zip

[env:nodemcuv2]
platform = espressif8266
framework = arduino
board = nodemcuv2

; Build options
build_flags = ${common_env_data.build_flags} -DSSID_NAME=HELLO -DSSID_PASWORD=WORLD

; Library options
lib_deps =
    ${common_env_data.lib_deps_builtin}
    ${common_env_data.lib_deps_external}
    https://github.com/me-no-dev/ESPAsyncTCP.git
    PubSubClient@2.6
    OneWire

; Serial Monitor options
monitor_baud = 15200

; Unit Testing options
test_ignore = test_desktop

[env:bluepill_f103c8]
platform = ststm32
framework = arduino
board = bluepill_f103c8

; Build options
build_flags = ${common_env_data.build_flags}

; Library options
lib_deps =
    ${common.lib_deps_external}

; Debug options
debug_tool = custom
debug_server =
    JLinkGDBServer
    -singlerun
    -if
    SWD
    -select
    USB
    -port
    2331
    -device
    STM32F103C8

; Unit Testing options
test_ignore = test_desktop