sprtt 0.1.0

• Added the seq_ttest() function, which performs sequential t-tests.
• Added the test datasets df_income, df_cancer and df_stress
• Added the vignette “How to use the sprtt package”
• Added the vignette “Sequential t-test”
• Added the vignette “Use Case”
• Added tests to simulate the error rates of the test
• Added unit tests
• Added pkgdown site
• Added logo