README: typo fix (#7)

* README: typo fix

Author: yunjunz

README.md

@@ -2,7 +2,7 @@
 
 This python 3 module estimates differential phase delay maps due to the stratified atmosphere for correcting radar interferograms. It is rewritten in Python 3 language from PYAPS source code and adapted for ECMWF's ERA-5 corrections. 
 
-WARNING: PyAPS3 could not work with NARR and MERRA weather models. Contributions are welcomed.
+WARNING: The current version does not work with NARR and MERRA datasets. Contributions are welcomed.
 
 This is research code provided to you "as is" with NO WARRANTIES OF CORRECTNESS. Use at your own risk.
 
@@ -20,17 +20,15 @@ or via `pip` as:
 pip install pyaps3
 ```
 
-One could also installed the development version via `pip` as:
+One could also install the development version via `pip` as:
 
 ```bash
 pip install git+https://github.com/insarlab/PyAPS.git
 ```
 
-Run the following to 
-
 ### 2. Account setup for [ERA5](https://retostauffer.org/code/Download-ERA5/)
 
-ERA5 data set is redistributed over the Copernicus Climate Data Store (CDS). Registration is required for the data downloading.
+ERA5 data set is redistributed over the Copernicus Climate Data Store (CDS). Registration is required for the data access and downloading.
 
 + [Create a new account](https://cds.climate.copernicus.eu/user/register) on the CDS website if you don't own a user account yet. 
 + Create local key file. Create a file named `.cdsapirc` in your home directory and add the following two lines:
@@ -56,6 +54,6 @@ python PyAPS/tests/test_calc.py
 
 ### 4. Citing this work
 
-The metholody and validation of DelayPackage can be found in:
+The methodology and validation can be found in:
 
 + Jolivet, R., R. Grandin, C. Lasserre, M.-P. Doin and G. Peltzer (2011), Systematic InSAR tropospheric phase delay corrections from global meteorological reanalysis data, Geophys. Res. Lett., 38, L17311, doi:10.1029/2011GL048757.