Gracefully handle read errors, check CRC

v2 updates:

• Remove Wire.begin from begin()
• Remove all Serial.prints from library
• Pass Wire in as a stream object into the library
• Change example(s) to run at 115200. Test if sensor.begin() was successful.
• Add link to library within examples
• Fix repo name to "SparkFun_Si7021_Breakout_Arduino_Library"
• Gracefully handle read errors
• Add isConnected() function
• Avoid hard delay(100) time waits. Poll, pass in max wait, or find other way if possible.
• Remove magic numbers
• Fix typos 'mesurment', 'makeMeasurment'
• Provide additional examples demo'ing any extra functions (ie, heaterOn/Off, changeResolution, etc)

Fix library name typo

v1.0.5

Update library.properties

Add bool return to begin()

v1.0.4

Update library.properties

PR to fix Keywords.txt

v1.0.3

Lib ver roll

PR to fix Keywords.txt

Merge pull request #2 from per1234/keywords-separator

Use a single tab field separator in keywords.txt